It's because this is mostly where people vent or need help solving problems so that is the part you mostly see. People tend to not write about the good things because good things don't upset them.
Then there are a few providers from time to time who aren't in this profession for the long haul or have just chosen the wrong career. It happens so you see their angst here.
Then there is the fact that you have not actually done it yourself yet on your own (no matter what your age). I think you'll 'get' this forum after you do.
I am retired now after 20 years of doing this and I feel it was the most rewarding profession I could have picked. I did something truly important. It's weird because I feel this way and don't see this forum as being negative. Stick around for at least a year after you start doing childcare on your own and I bet your perception will be different.
Like someone else said, it happens in other jobs as well. I'd say all jobs. People just complain about the parts that they don't like but don't mention the parts they do. It is human nature. No mystery there.
Laurel