I don't think passkeys are going to replace passwords any time soon, and I don't think freeloaders are even part of the equation here. You can share a passkey through Bitwarden just as easily as you can share a password.
Freeloaders already need to jump through hoops to share passwords and even then they're getting off easy; if streaming companies actually cared about catching freeloaders, they could stop the practice all together. What they're doing now is just signalling them that you're not supposed to and adding very minor annoyances to the mix.