Caveat. This is not a slam on the OP, it's just my opinion on this whole looping thing.
I've played bass with some fantastic musicians in my life (some even went on to be famous). What that has taught me is that I'm not even a beginner drummer, only a passable rhythm guitarist and a novice keyboard player. But, I'm pretty sure I know what I want good drums, guitar, keyboard etc. to sound like.
Every band member has almost always learned that the band is only as good as its weakest member.
So what am I supposed to do if I want to compose a song but my skills are not up snuff? I could collaborate, and I have.
But sometimes I just want compose a song and not wait on collaborators. Now what?
Enter EZKeys, MIDI drums patterns, guitar loop libraries and (gasp) the high end Band In A Box with Real Band (i.e. real players). These tools are heaven sent (IMO) for the composer who is not skilled enough to play what is heard in the head. And as my man Mesh says, sometimes these tools are nothing more than a gateway to the completion of a song by collaborators.
So for those purists who can do it all, I salute you. Feel free to look down on anyone who chooses to use such tools. Most of us won't even feel the **** you're attempting to put in our armor.