I use iMessage. It's great, and doesn't get in the way. And as I said it's included on my phone. It also allows me to communicate with anyone and I don't have to think about if the person I'm contacting has it installed or not, it gracefully degrades to SMS when needed. That's a great messaging app!
While I do have browser tabs open for WhatsApp, Google Chat, and GroupMe, as well as the Signal desktop app running, most people I know do not do this, and do most/all of their messaging from their phone.
I get that's not your experience, but it is indeed an experience that exists, and is probably fairly common.
For this reason alone, I greatly prefer iMessage/discord/slack/whateverIsNext so I can use it on my phone and my computers.