I see the similarities, but one thing is different. With guitar and bass amps, some of the vintage gear actually sounds as good as gear that's available today, and in numerous cases, has a unique tone character that can't be easily replicated.
Think of an original Ampeg B-15, for example. While not too many gigging bassists are going to be playing live shows with them, they're still hugely popular in recording studios of all sizes, from amateur home studios to the most prestigious commercial studios, and everything in between.
It isn't just nostalgia causing this. In many instances, that signature B-15 sound can best be achieved by using a genuine, vintage amp.
Sure, you can buy a modern day amp that will sound almost exactly the same, plus will be more durable and reliable, but the reality is that it will almost always be a modern reproduction of the exact same vintage technology (with a few modern improvements for additional useful features and for durability). It's also almost certainly going to be much more expensive than buying a vintage amp in good working condition.
Contrast this to modern day digital cameras as compared to vintage film cameras. Within the past decade, digital image sensing technology has far surpassed film based imaging in every way possible way. Literally, the only reason to choose film over digital imaging is for nostalgia purposes.