[snowwrestler]

This question may be easier to understand in the general case: why don’t people do everything themselves?

Why don’t people paint their own houses? Why don’t people fix their own cars? Why don’t people sew their own clothes? Why don’t people cook their own food?

Of course a lot of people do do these things themselves! Just like a lot of people do use free and/or open source software tools.

But a lot of people don’t do these things, at least not all of them, and probably not all the time. If you can think of the reasons you pay for things you might be able to do yourself, you can start to understand why a business does too. It usually comes down to opportunity cost and specialization—answering the question “how is my limited time best spent?”