Srry, I'm getting a bit sick of the required bs accounts(idling to be hacked someday) for all kinds of crap on the interwebs.
Understandable. That bugs me, too. But the problem is much deeper.
TL;DR: Would be of course nice, but in the current state of Factorio it is the better choice for everyone.
To do something like that it requires a kind of technique called single-sign-on.
Which is state of the art, and of course the Factorio-Server can do such things. But this is quite difficult to implement with
existing software, which has it's own user-account management, cause if software is not developed for that, changing it to single-sign-on is really, really hard to implement and a very dangerous source of common security-problems.
Believe me or not: You don't wont to have phpBB changed to single-sign-on mechanisms. It's like filling diesel into a gasoline motor. Last year I digged deep into the phpBB-source for wube in Prague to find a lot of problems around this subject. The same with wiki (much easier) or now with the mod-db.
It is in that cases much more elegant and safe to change the software so, that it uses the single-sign-on only to verify the user credentials on registration and then leave the whole user-preferences in the hand of the application.
And it has also a big advantag to do it like so: Only with the first login the user-data is transmitted into the other software and from there on it could be changed independently from the origin. That removes a lot of problems. You can work much more agile. Changes can be done much faster, because you have no side-effects and you cannot destroy anything important. Not all accounts are on every service and if, it is likely that they have different passwords. So stealing all accounts in the mod-db is not a horrible fail.