The Internet works just fine when it's decentralised, but particularly with e-mail, relying on the big service providers (or an ISP-provided address, for that matter) immediately locks you into someone else's systems for no particularly good reason.
Registering your own domain and setting up mail forwarding can be done with any number of services and costs less for a year than many people pay for a week of their cell phone service, and crucially, the domain is registered by some specialist service but is your domain and can be transferred to another service any time you want.
Unfortunately it can be a scary-looking process for non-technical users, but for those with enough confidence to arrange it, I highly recommend it.