I am not sure when this happened, but NBA 2k17 is no longer able to be purchased via Steam. I feel this was recent and perhaps coinciding with the release of NBA 2k22.
Luckily, I already had it purchased, but I had to purchase NBA 2k16 through a third party for this reason last year. I wish they'd keep these games up, but I am sure they have their reasons. Something to keep in mind for people who had their eyes on NBA 2k18 , NBA 2k19, NBA 2k20, etc. in the years to come.