It's like running your own email server in the early 2000s. For large businesses it totally makes sense.
Hobbiests can do it to if they are interested.
Most people will land at a "shared" service and let someone else handle the admin tasks. I'm afraid that eventually there might only be "outlook.com, gmail.com, and yahoo.com" so to speak, because it's just the easy way to go for most people and economies of scale make it more feasible for the operators who find ways to get paid.