It's about the look and the image for many, if not most. Vintage is the new black. it's what' "in" these days. In a few more years everyone will one some brand new space age looking thing. Although I would say that the wood could be a big factor. Electronics - back then, they were inconsistent and cheap, but that works for some because they like the "rubber band on a shoe box" tone
You want a vintage look on the cheap?: Buy a used squire for $100, remove everything from the body, then take said body and drag it behind a pickup truck down a gravel road, spill a bunch of beer on it and then leave it out in sub zero weather in the back of the aforementioned pickup for a few days and then bring it back into a nice warm room so it heats up quickly to create a plethora of beautiful cracks in the finish. Good chance when you put it all back together it will sound and play nearly as poorly as a vintage instrument!
I still have my "vintage" 77/78 P Bass that I paid about $325 in 1983. Replaced the lame original p/u decades ago and considering a newer "vintage" (i.e alnico, passive) sounding p/u. I'm have no fear of playing out with it as the damn thing has seen its share of abuse over the years. It looked new when I bought it and now it looks like Jaco's well worn infamous jazz bass. If it got stolen I wouldn't be out $2500 or whatever some sucker would pay for it because I only paid $325 and would never sell it anyways. I don't play it much because the frets are pretty worn down and I love the tone of my Spector NSCR4. But I will bring it out to a gig if I want to look "cool".
Bottom line is the general audience doesn't really care and can tell the diff between a true vintage or a quality instrument. As we know most don't even know the difference between a bass and a guitar.