Why so? They just haven't jumped on the meme-tech train, at least wrt to this setup.
Running an actual process on an actual server has been around since time immemorial, as has doing the "atomic" deploy thing (which I'm guessing is just updating a symlink from cold to hot).
The way it works best is when you have multiple accounts ,you have a single Identity account, which is where your user accounts live. This account basically allows sign in and assume role - oh and you can't assume unless you have authenticated with MFA.
Then, all your other accounts - dev, prod, service, whatever - simply have roles and no user management overhead - i.e you aren't duplicating users in a bunch of accounts and having to deal with a bunch of different identities.