I've got twenty minutes to kill while some downloads...er...download so I thought it only fair to answer as well since you folks have been so open and enlightening.
 
First, I started playing and taking lessons at a very early age (4).  No foolin.  And I've continued on as this surreal life has passed me by.  So this music stuff is kind of ingrained in me.  Second, I'm pretty competitive by nature. And by that I mean If I actually do get off'n my lard ass and do something...I've got to try and do it as good as anybody else does it or face my own sense of crippling self doubt.  Which, as it turns out, I've been able to (mostly) avoid seeins as how I was born a self-absorbed blow hard with a messiah complex.  Plus, it turns out I do happen to love music near to death.  Alright then.
 
As some have alluded above, I sensed early on that it was also an easy way to attract females and guess what?  No, go on guess.  It actually does!!  So...until I met and married The Bear I was an unmitigated and unrepentant poon hound as well.  So I had that goin for me too.
 
But back to music and why I do it:  Peer group acceptance.  Pure and simple.  Oh sure, I've made a livin at it as well for lo these many years but that's always been secondary...if not by much.  In fact, those folks who'll spend seeming eternities on learning and producing in order to recoup not one red centavo simply mystify me.  But I'm sure that's just because to me it's always been a "job" as well as fun.  Don't get me wrong though...because it IS a job some of the time it can also be pure drudgery.  And how.  I actually envy you fellers and gals that just do it for enjoyment alone.  You're on to somethin.  Or maybe you're just ON somethin.  Hard to say which.
 
So, for my songwriting and producing, peer group acceptance it is and always will be.  But the key, of course, is the peer group a feller shoots for.  Mine happens to include folks like Randy Newman, John Hiatt, Hoagy Carmichael, Harold Arlen, Lennon and McCartney, George Martin, John Leventhal, Phil Ramone...you get the picture.  So...as you can see...most of my work still lies before me and I've still got a long hard road to travel.  Who knows if I'll ever get there?
 
But, hell, what else I got to do??
 
 
 

Ya, we're all there with you!
 


 
(Damn that Pope Jon Bouy pic cracks me up everytime!  )

Of all the imitators, I likes the Beagle the best.

yorolpal 
But back to music and why I do it:  Peer group acceptance.  Pure and simple.  Oh sure, I've made a livin at it as well for lo these many years but that's always been secondary...if not by much.  In fact, those folks who'll spend seeming eternities on learning and producing in order to recoup not one red centavo simply mystify me.  But I'm sure that's just because to me it's always been a "job" as well as fun.  Don't get me wrong though...because it IS a job some of the time it can also be pure drudgery.  And how.  I actually envy you fellers and gals that just do it for enjoyment alone.  You're on to somethin.  Or maybe you're just ON somethin.  Hard to say which.

I think the acceptance thing, and acknowledgment, may be a big part of it for those of us that don't make any money at it. Everybody likes to hear an attaboy now and then. And it's kind of cool to put your name on something that people can experience, and hopefully enjoy. Sometimes, that is payment enough.
In my day jobs (15 years as a journeyman plumber, and now a cable technician), the idea is to make my work as transparent as possible. As a plumber, I took a lot of pride my work. And outside of the inspector and my associates, nobody would ever see it. If the end user never knew it was there, I did my job.
All said and done, around 2000 home owners and businesses with one less thing to worry about.
A proud but silent legacy.
But I have the arts. Like so many here, music, painting, etc is just something I have to do. I can't not do it.
Yes, it can be a lot of work, but if I didn't enjoy it, I wouldn't do it.
And when it's done, there is something you can see or hear or touch. And my name's on it.
At some point, I am going to die, but my daughter will be able to say,"This is what my dad did".
I suppose my short term goal would be to have people be able to enjoy what I have done, but my long term goal is to leave her with that.
 

Some of the things already mentioned definitely apply to me:
1. To try out ideas that have been rolling around in my head.
2. To influence other musicians.
3. It's a learning/discovery process.
4. I enjoy messing about.
5. Just for the hell of it.

I seem to be where I'm supposed to be, in a place where I can play live and call the shots and for a very good cause IMO (in church). I think this has been good in a number of ways. It helps me to fulfill a quest,it sharpens my chops,it helps me to work with people in a musical way. I would do that if computers and recording had never been invented and if 30 or 3000 people show up. The other music I play offline at my other venture is mostly all copyrighted so I don't tend to play much of that online in a way that could hold me liable, although I work on some original music in that realm too.
 
When it comes to recording and playing on my DAW  there are no rules. No one needs to follow or even like it and I like that freedom. So I'm free to make weird crap no one else on earth will like LOL.
 
It is freeing to create my own objectives and pursue them.We musicians are a dime a dozen on soundcloud,reverbnation and others and i know that.I don't have any lofty ideas.
 
It's nice if someone likes it but I would do it anyway, it's nice when it resonates or connects in some way to someone else.I can appreciate the effort others put into their own works. I love the songs/technical and software forums in the ways that we can help one another to make better music . We have some good people here.
 
I have some small commercial pursuits in the works but I'm not betting the bank on any of it. If I never made any money at any of it I would still have a lot of GAS,would still be wasting inordinate amounts of time in my studio and enjoying it.
 
It's mostly what we do I think.