There are plenty of rough edges that apps are able to buff out that a browser cannot.
I use plenty of things in a browser, but if I'm gonna scroll something daily... I want that image viewer with tap slide zoom. I want that specific folder that the app saves shit to instead of just "downloads". etc. etc.
Having a dedicated app is just more convenient in most cases. And apps generally offer more features and QoL improvements compared to a site. After using memmy for about a month I can’t use the official site, especially on mobile.