Well, largely, the problem that I've seen with older tech, especially CPUs, is that obtaining actual NEW motherboards for them, is really spotty. It's not so much performance issues. Heck, if I could still get Core2-era mobos, NEW, for like $40 that weren't some off-brand from China (like a nice Gigabyte G31/G41 micro-ATX board instead), then I might still build some E8400/E8500/E8600 rigs for people. Performance of those chips wasn't horrible, and it's only up until Kaby Lake Celeron, that their lowest-end chips compete in frequency with some of those old-but-goody (at the time, higher-end) Core2 CPUs.
But like I was looking on ebay last night for mobos, and I saw some Biostar B150S1 boards from not-so-big-league dealers NEW for $44.99 FS. Not too bad. Not as good as the four I obtained from Newegg for $28 shipped, after discount and 50% off promo code one time, but still, a decent price, cheaper than the $55 for a B150 MSI board refurb that you can get from Newegg on ebay right now, or $60-65 for the cheapest NEW B250 boards on Newegg.com. Back to the point, you can get NEW KBL Celeron CPUs for less money than you can get Skylake Celerons, even when they were current. $43 or so. So $45 for board, $43 for CPU brand-new retail-boxed with heatsink, and maybe $50 on sale for an 8GB DDR4 DIMM, so $150 for board+CPU+RAM. And it's upgradable to an i7-7700(K), should the user ever want to. (But I generally buy the Kaby Lake G4560 CPUs when I can get them for under $65, they perform so much better than the $43 Celeron CPUs, that it's worth it, especially since I can turn them into budget 1080P gaming rigs for an $80-120 GPU.)
That's what got me to buy those FM1 boards and CPUs, because they were so inexpensive (CPU + mobo + heatsink for under $50), because they were all NEW, and FM1, though short-lived, wasn't too bad. And true to what you said, waltchan, those boards were fully-supported by Win10, just install, go online, and it finds ALL the drivers for those boards. Now if only Win10 licenses were cheaper...
Edit: And then there's the issue of RAM capacity, and availability.
Those older but decent Gigabyte G31/G41 boards, took two slots of up to 2GB DDR2, I believe, limiting their overall RAM capacity to 4GB DDR2. I think that chipset supported DDR3, so more modern variants could use 2x4GB DDR3, limiting total memory capacity to 8GB, but that may still be too limiting several years down the line. (My DeskMini units have 2x8GB DDR4-2400 in them, and I caught Waterfox 53.x using up to 10GB of RAM, all by itself the other day. So the days of 8GB systems may be limited. Also with gaming.)