Because 'Teams' isn't just a simple meeting application. It's very feature rich. If you ever have to deal with the admin.teams.microsoft portal you'll know how many options and toggles it has.

Alongside this many businesses deploy 'Teams Supported' or 'Teams Enabled' devices into meeting and conference rooms. Yealink is a popular brand, they don't have baked in support for LibreMeet or whatever meeting products exist.