[7steps2much]

Just my personal opinion, but the reason I got a domain to start with was to not be dependent on a specific provider.

Also, it's is far nicer to be able to simply sign up to a website with [e-mail] than go generate a random email. Especially if you are on another device.

[M5x7wI3CmbEem10]

doesn't this lock you in with the domain provider? google domains or whatever you use

[neoromantique]

You can migrate your domain to a different registrar

[encryptluks2]

Using a custom domain is precisely to prevent lockin that you are getting with many of these alias providers. If you don't own the domain then you can't migrate to a different provider.