My son wanted to login to the desktop AirBnB because I wanted a PDF of a receipt, which he couldn't get on mobile. He logged in using his Google account on his phone. On his Windows and Mac laptops, with Chrome and Firefox he got errors. He just couldn't login. We cleared cookies, everything. Rebooted. Nothing would fix it. Of course, to start a chat with aBnB you need to login...

So, I agree. Every service should have separate credentials.