The Steam client is not much more than a glorified browser. Steam could make it a lot faster if they saved images instead of wasting bandwidth by downloading them over and over.
This makes the client app slower than molasses when the internet is bogged down. The profligate waste of bandwidth is a problem for those with mobile internet etc.
We are aware that Steam expects world+dog to have unlimited high speed internet but that is very unrealistic. Many internet providers limit the amount of data used.
So besides being a slow poke and wasting bandwidth. The lack of images means the offline mode does not work right either. Images are needed to be able to recognize the game that a player might want to use.
The Steam client uses an embedded version of Chrome. This part of the problem.