It probably has to do with the fact that a lot of people are patient enough to wait 10 seconds for something to finish if a) they understand it and b) it does the job.
The average person will put up with a lot of friction to use something they're familiar with and needs a lot of incentive to change. If your thumbnails fail to load every 10000 times or every 100000th profile picture upload fails most people will just retry and hope it works the second time, not find a different service or app to use.
The average person will put up with a lot of friction to use something they're familiar with and needs a lot of incentive to change. If your thumbnails fail to load every 10000 times or every 100000th profile picture upload fails most people will just retry and hope it works the second time, not find a different service or app to use.