You can still get brand new generic motherboards for old CPUs.

I swapped out old ASUS MBs for an i3-540 and an Athlon II X4 with brand new motherboards.

They are quite cheaper than getting a new kit, so I guess that's the market they cater to: people who don't need an upgrade but their MBs gave in.

You can get these for US$20-US$30.