Im not the OP and not sure about multitude but one problem for a successful app is bandwidth usage from transferring redundant chunks of HTML, and potentially JS and CSS
Assets like JS/CSS can be cached, and unless you're doing something very convoluted HTML overhead should be pretty low. I mean HTML was standardized in the 90s when we had <100Kb/s (not KB/s) bandwidth so i understand if you have a "successful app" you're always going to need to deal with scaling, but it's not exactly a problem for most of us and caching reverse proxies are very easy to operate and stable nowadays.
So you’ve said that you don’t have this problem because your not a successful app? Or are you denying that there’s duplicate HTML, and sometimes JS and CSS being sent? 100k for 100 users is 10mb and bandwidth is one of the easier ways to save costs.