That’s not even true, I run my own mailserver for private and a business and it works like expected.

Yet people claim it writes all their programming code…

The analogy is that you buy a car (because if it breaks, the car and your entertainment stuff, you will buy a new one to replace it, you will also carry all maintenance) but suddenly you can’t drive backwards anymore because the manufacturer decided retroactively that you should pay extra for that (possibly in a subscription).

I would say it is your good right then to make your car drive backwards regardless of what it may take.

The load distributes across more shoulders automatically.

If you only host a server for yourself and 10 friends it costs next to nothing, if you have a big operation it can get just as expensive, it depends on what you are willing to do.

With centralized systems there is no choice but for the one centralized host to host everything.