The whole Slack deal is to get away from desktop apps and run on the browser.
This opens up freedom to start Slacks where corp is blocking app installs (but not zealous enough to be blocking/MITM'ing network yet).
Click there, get Slack. No risk of accidentally closing it or losing it somewhere.
Have you ever need to switch between multiple tabs semi regularly while keeping other tabs open? Have you ever wanted two tabs to be side-by-side? It's a usability horror show.
Wrapping Slack in its own app let's me use the windowing manager my operating system came with.
It's a workaround that I do use but it's not a substitute I'm afraid. Windows handles this a little better, IMO, but it's still not great and the occasional crash of a web browser tab still sometimes takes the whole thing down.
It's so easy to separate tabs into their own window and utilise the window managers control.
cmd+` to switch between different Chrome profiles/windows
option+shift+a/d to snap window to left or right
tiptap to switch between tabs when using trackpad
when slack notification comes up, just click on it and it takes me to the right Chrome tab
I do agree we need a better way to integrate tabs in native windowing