Honestly, I have no idea what business Steam has starting for whopping 5 seconds as it is right now (after the 'speedup').

It is a simple shell for launching already downloaded apps. This is disgrace and nothing to boast about, especially considering Valve takes 30% cut of basically PC gaming marked for making it.

It's way more than this. Some may argue about how useful all of these features are, but Steam client is also a store (with lots of personalizations), a social network (forums, text and voice chat, personal profiles etc), a mod hosting platform, a game review site, a digital marketplace (cards and items. You may be surprised how popular this aspect is). It also does the controller remapping, manages cloud saves and screenshots/videos, allows to store games at several locations at ones. It provides games related news, checks for updates on all of the installed games.

Again, one may argue how useful all of this is, but it is there, and most users likely have the app on a OS startup anyway.

Unlike nearly every other platform that takes a 30% cut, you're not forced to distribute on Steam.