That's only true until you've quit and done your own thing for a while. There are benefits and drawbacks, it's not for everyone.

I for one prefer focusing on engineering and team building over sales and marketing, which means that to "do my own thing" I end up spending half or more of my time doing things I don't enjoy, which is just not worth the headache.

If I had a significant cash reserve I would probably have a lot of fun building a product in the context where you didn't have to grind for every dollar... but that's also just known as a hobby I think.