The big cost to doing it yourself is maintenance.
There is, for a lot of people, a fairly large amount of value in never having to worry about hardware dying. If it does, that's someone else's problem, and it will be fixed, as far as you are concerned, rapidly and without any interaction with you.
How much any given person values that is going to vary wildly, but it means that you don't risk having stuff go down at a moment when you can't do anything about it. Maybe you're on vacation, and you don't have any hands that can do anything. Maybe you're sick, or just extremely busy that week.
You're not wrong that this comes at a fairly substantial monetary cost, but it is wrong to say that this isn't, in many cases, a cost that people are more than willing to pay in exchange for the benefit.