Larry, broadly speaking I agree with you.
I managed to use computers for 35 years without owning a Mac, it's only collaboration with people who only use them and Logic/Mainstage that got me to get one (low end iMac) in the first place last year.
Apple's approach to backwards compatability is indeed poor. Not that PCs and Windows have been immune to the same thing. When the original pentium cpu was launched software rapidly began to appear that simply would not run on a 486 chip because it required the pentium instruction set. ISA became SATA and PCI has undergone several changes over the last 20 years with old hardware becoming incompatible. The move from 16 bit to 32 bit left quite a lot of old software behind. Now we have 64 bit. The system requirements for PC software have steadily required more powerful PCs for optimum performance. Even the current version of Sonar isn't compatible with older versions of Windows.
One of the oddest things about Macs is that the fixed design (in some ways a strength), which is then manufactured for a period, means they are never cutting edge in hardware terms and a PC built for the same (or less) cost can usually hammer a Mac in terms of brute processing power. Macs are prettier though.
Yet, as you say, there are people who have an almost religious cultish attachment to Macs. I know people who still use old G4 and G5 Macbooks that are almost museum pieces but their owners have an emotional attachment to them that's hard to break. Personally I can't imagine having an emotional attachment to a computer so strong that I would ignore a decade's worth of technological advance, but obviously some people do. And there are the true believers, people who wish to be seen as "independent, creative, free-thinkers", who queue for hours or days to get the 30 seconds of glory associated with being the first to own the latest iGadget. Never underestimate the "cool factor" as a marketing tool.
You're right about the 1% reference, but the consequence of the 1% is that almost every time you see a computer on stage it's made of light alloy with that big, glowing Apple logo visible to all. So aspiring musicians get to associate Apple with being the computer of choice for musicians, and in turn will tend to buy Macs.
It's the same marketing logic that lies behind Roland, Korg or whatever written in big letters across the backs of synths, Marshall's black with gold control panel, script logo in white and distinctive 4x12s, even Leo Fender's 1950s tweed and big Strat-style headstocks. If potential customers see what they regard as successful people using your product then the next layer of musicians down from the 1% will be inclined to follow suit, and every time a customer sees your product on stage it reinforces in them the feeling that they bought the right thing. So next time they'll buy another.
As for Sonar, I think Cakewalk are correct to not develop a Mac version (having said that they'll now prove me wrong and announce on :-/ ). It would mean two code bases, two different sets of bugs to worry about and so on for potentially little additional return. Better to be the best PC DAW, with the best integration with the hardware and Windows than yet another Mac DAW trying to enter the market and compete head to head with the established players.