My guess would also be that the younger the player, the more that matching racquets and bags means to them, not that plenty of older players don't match.
I used the Prince bag from my youth for about 20 years (I'm 35) (I still have it, but it's pretty shot) no matter what brand of racquet I used - Prince, Dunlop, Wilson, Head.
I currently use a TW 9-pack -- a nice bag, but not the best. But, I got it so cheap when ordering racquets, it was hard to justify spending $50, when I could spend $10. In fact I have 2 and store frames in the other one.