Me too. I've had new ukuleles (say, built in the last 20 years) but they don't seem to stick and are the first ones to be sacrificed when I have to sell some.
It has nothing to do with monetary value: a late 1990s National Reso-Phonic went out, and I've kept a cheap plywood 1970s uke for the last 10 years. Although 'old' seems to hold its resale value a little better than 'new'.
It also isn't really about musical value (sound, playability), because the Polk-a-lay-lee is frankly unplayable (you can squeeze tunes out of it, not much more) while the national and even some magic fluke ones I sold were pro instruments (as in, you could use them for making a living out of music, or blend in with a serious band).
I think it's because I like old stuff in general. I even like a worn chair better than a new one. Prefer a wind-up clock to a digital one. The illusion that something that survived decades must be of a good quailty, perhaps? (not always true: some old stuff is well-preserved because no-one ever liked using it - why did that stuff end up in the attic anyway?). Yes, they had better wood supplies in the olden days, and wood does open up, and labor was cheap so time was taken during the manufacture, but seriously if you blind-test a 300$ antique uke against 300$ new one I wouldn't dare to take a bet. Play that old Dobro slightly wrong and it starts buzzing like a bee.
Perhaps it's also because older instruments are a bit dented and scratched. I'm clumsy, and it's heartbreaking to make the first scratch on a new instrument. But hey, when someone broke it in before you, it's easy! I don't have mint antique ukuleles, some of them even underwent major surgery. I don't mind taking even the expensive old ukuleles out, I've had 8-year olds playing my 1930s Gibsons and tiple (okay, fair, I did tell first them not to smash them).
But I think the main reason is rarity, and that I like to stand out. Silly really. Not having the same ukulele as my neighbor, you know. Although my neighbors don't actually even have one.