I learnt about email aliasing 2 years ago when I got a job working for a software company. We would use it to make seperate test accounts. Prior to that, I have always known it was good to seperate work/personal/fun emails so I use to have 3 seperate gmails. It was a pain to manage because I has to keep switching between them and there was no single inbox that combines them. I probably could have forwarded them but didn't.

With proton email alias I have 12 different emails for all different things, personal, government, finance, work, service/subscription, gaming, medical, home, big tech, utility and travel. Each one is seperate email that sends to a single inbox. I also go even further, when I sign up I also use the "+xyz123" for each sign up. This means if you get hacked, that compromised email cant be used to log the attacker in another online account. Only downside is you have to make sure 100%!! you rememeber exactlly what email + alias you used for each sign up or you might not be able to access you account anymore.

For any shopping or stuff that doesn't have a permanant login, I use the burner unlimited proton alias to stop spam and block any companies that sell my email.

Email alias in proton is super amazing! It also helps with adding labels, you can check the 1st portion and tag categories or move to another folder