I'm currently signed up to ten or so different source code web services hosting FLOSS (e.g. KDE, FreeDesktop, Debian each have their own instances).
Attrition has held me back to participate in discussions or reporting issues. For that you need an account, and some source code web services make 2FA mandatory, and often I need to reauthenticate and go through that flow. If I'm exhausted, my brain makes the decision that it's not worth the effort.
A couple of other other reasons come to mind as well: setting up your account properly (adding SSH public key), setting up yet another entry in one's own
password manager, acknowledging that their will be additional mails going to my mailbox (transactional e-mails, maybe important informational e-mails such as data leaks, TOS changes, etc.).
Fast growth of the project isn't our goal and definitely doesn't override our collective ethics. If someone will only send PRs via a proprietary Microsoft platform then maybe this isn't the project for them.