The only reason people can do that is that they have a different profile on an xbox or playstation. If you do it on playstation you have to pay for a seperate ps plus subscription, but as far as I know on xbox it is shared amongst all accounts on that device. It makes it very easy for people to create multiple accounts for rtgs and so on. Personally, I use playstation and I'm not paying twice to play online so only use the one account, but I also keep a tonne of my players rather than do expensive sbcs so I have no issue with variety of players available.
