This is an annoying but important UX issue. If you have any sense at all, you use something like 1Password to sync and encrypt passwords.
Explanation for other beta users (the dev team probably gets this right away)
Zwift (on Mac at least) logs you out on quit, so you have to enter your password on every program launch. Without support for copy/paste users will choose simple, easy to remember passwords, or the one they use for other services, which places that password at risk - even if zwift stores it on the database as an encrypted string which they most likely do - in the case of a data breach. We can assume that it is not if but when a system is exploited, so your best defense is to never use the same password twice for two services, and change them often.
please, please, please allow the clipboard access to the password input for both registration and login, or at the very least, persist my session across application launch.