Surprisingly large number of businesses run on whatsapp, as a consultant in Asia it's prob around half the businesses I've worked with prefer it over teams/slack. If Meta had been sensible about API access Telegram wouldn't have even got a foothold.
WhatsApp vs Slack + Teams is a bit of an apples to oranges comparison though.
I had a look at getting same agent up in WhatsApp but it seems to need FB business acc to even start process, to get FB business you need an FB personal etc. ... looked like too much effort