For me it’s a usability thing—I tend to lose track of SPA tabs, often by closing the window or not being able to differentiate them from content tabs. I do use web apps but I vastly prefer using my machine’s window manager and window buttons/lists.

I personally use a 3rd party client which uses actually native code rather than electron https://cancel.fm/ripcord/

The site also is a heavy resource hog but you're right that it's overall less.

There are plenty of lightweight clients that use the Slack API. I don't see why people complain so hard that the official client is heavy.

Weechat with Slack is a dream feels like the good-ole IRC days.

Using lots of browser tabs instead of applications appears to me to be a step backward in usability. Instead of relying on the window manager to organise your work, you add cognitive load instead.

> Why does anyone use the app instead of the site?

Because on Android at least the website detects that you're on a mobile device and switches to read-only mode. Correct, you can't even post a reply without fudging user-agent or installing the app.

Why would I hide my chatrooms in several browser tabs? Sounds maddening.

Can't make calls through the site with Firefox