I didn't really think about it given I had Steam for years. But it's not like Sega makes these tidbit games regularly.
Streets of Kumorocho and Golden Axed were released to promote Sega 60, but honestly these games felt like scrapped games.
Like, Streets of Kumorocho was probably going to be that one arcade game in the Yakuza game at the time but got cut, so they just released it on Steam and regard it a special promotion thing.
Steam gamers always had it good when it came to SEGA birthday.
I remember SEGA gave away Sonic 2 and also NiGHTS into Dreams for free on Steam on their birthday.
(which kinda make Yuji Naka annoyed since those two games are happened to be his co-creation and SEGA gave them away for free).

While it's just kinda like mini games, Streets Of Kamurocho and Golden Axe were also Steam-exclusive.
SEGA usually left the console/mobile fans on their birthday celebration (other than sale).