Which is a bit ironic, considering all of these are in two compilation packs.
They're probably going to have a new compilation pack that costs about the same price and has a few additional games...but they didn't want to just sell DLC/standalone games for the Collections that already exist.
And actually, a lot of these games that are getting delisted can be purchased separately. And maybe even have ROMs that are easily extracted. So maybe they just want to lock things down into an all-or-nothing ROMs-hidden collection or 10.
Exactly, they announced earlier this year that they were working on reviving a bunch of licences, including Crazy Taxi, Jet Set Radio, Shinobi, Golden Axe, Streets of Rage, and hinting at a longer list. We don't know yet eactly how many titles that includes, and which of them will get remakes, remasters, or brand new games, but it was hinting brand new. Early dev footage was leaked at some point for Crazy Taxi and Shinobi.
They already did this with the classic Sonic games (Sonic Origins) and removed them from any new Steam copies of the Genesis/Mega Drive Classics collection. I doubt they're working on all the games in their library, but it may be enough of them that they just decided to pull the whole collection rather than leave it so gutted out. Sucks, but yeah, that's the way it goes. That said, Shining Force remaster please? That would be awesome.
I wonder if it's a licensing thing. I know a few of these games had heavy use of licensed music, like Jet Set Radio and Crazy Taxy. At least, the original versions did, I'm not sure if that's the case for the Steam ports.