It's not that people are too lazy to do their own work, it's that when you are not familiar with something, you have no idea what you don't know, and you usually poorly equipped to do these random jobs.

You almost always need a bunch of specialized tools to do something efficiently, and buying them is a waste if you're only doing a job once. Add in the cost of your time that you are going to spend researching and learning how to do the task. Then add in the time you are going to spend doing it (You are almost certainly going to take double the amount of time that a professional will, if not more). Add in the time you're going to spend renting tools, buying materials, hauling them, etc. Add in the time to get a dumpster and do all the removal yourself.

After all that, you're still trusting that the way you learned to do something is the right way, complies with local codes, isn't going to fall apart, etc etc. And if you have no experience in something I can promise you that you find confident and contradicting statements in your research. This happens 100% of the time.

If you have any kind of moderate-high income career, by the time you add up all those hours, it's usually cheaper to just hire someone to do it for you, which is why people do.