Email is a collection of different protocols: SMTP, IMAP, POP are all different protocols that serve different purposes. Oversimplifying a bit, but - SMTP is used to exchange messages between mail servers. IMAP and POP are used to synchronize mail between a mail server and a mail client.

In other words, they absolutely can shut down IMAP and POP but still send/receive for gmail.com addresses. The main reason reason they wouldn’t do this is that their larger clients on Google Workspace need that functionality, but it’s the type of thing you might imagine them taking away from the unpaid version of Gmail to nudge companies over to Workspace.

They are most useful during local development. It’s useful to have project-scoped config that your app interacts with in a manner identical to how it works in prod.

Generally you don’t commit to version control because you want to keep secrets out of there. However, it can be sometimes useful to hold non-sensitive config that you may want to commit but also to customize on prod. For instance like NODE_ENV, so you’re not building multiple mechanisms for configuring your code. But this is less useful and generally solved with a sample config that is copied to the .env file that is never pushed to VC.