But, Why do i have to practically re-load every single thing every time i load the steam client ? Surely (if this is not just a setting i am missing somewhere) is this not a total waste of valve's bandwidth ? and multiply by millions of users is a waste of ISP bandwidth not to mention, energy wastage through computational & network power required, not to mention a waste of time waiting for these things to load each time. It's probably one of the added factors as to why Steam UI is so sluggish also..
why do i have to load the game thumbnails in my wish list every time i boot the steam client ? I have 200 items, it takes around 1.5mins and around 150mb of data and it stalls the whole app whilst loading.. each and every single time (again multiply this by millions of users every week). If im offline i could understand, it could just place holder a blank list to remind me of what i wanted to buy, should i use the web client instead but no, you just get a blank 'Error code: -106'
why do i have to load the game thumbnails for games i already have installed on my Collections surely this should be inserted on installation ?

i kind of expect the answer to be the same as the sludgy web answer for why the UI is slow. But surely, if this is the case you could have a setting to Cache your wishlist, collections and other minor web UI elements to speed things up. On the rare off chance a game changes its cover art why not write in a one line of code which checks for anychanges = yes / no and if no just keep the cached image. Games and steam already eat a lot of space so caching as much as possible should really be the sensible option.