Using your own domain also has advantages in terms of being able to use aliases for different websites so (when, not if) an address gets leaked you can > /dev/null it.

If you're cheap like me you can give family members their own subdomain so everyone can have aliases for the cost of a single domain.

It's sad to think back on myself nearly two decades ago when Gmail first launched as invitation service and I thought I was being smart by not paying for my own domain, little did I know how evil Google would turn out to be in terms of locking people out of their own accounts with no recourse.