Why do people assume you just don't try hard enough?

It seems like most people just cannot believe you can work hard and achieve nothing.

Their world-view depends on a certain degree of fairness and autonomy. Therefore they believe absolutely that if you work hard at something you'll succeed. They believe it to a point that if you haven't succeeded, they will by default say you haven't tried hard enough. It's circular reasoning at its worst...

I see this all the time in subreddits where people express thier frustrations with being single. A lot of the people commenting immediately assume the OP is simply not trying hard enough, needs to do XYZ, or even worse assume there are flaws in the OP's character. As if they had not tried all those things already.

Over the past 15 years I tried: getting in shape, improving my sociability, expanding my social network, getting a good job and make decent money, ect. All the things people told me would work to find a partner. It never happened.

The only thing left at this point I can think of, is getting very extensive cosmetic surgery that costs a small fortune (last surgeon I talked to quoted me about $80,000 - $120,000), to fix my very apparent facial flaws. But I'm not in a place in my life right now where that is even remotely affordable. And at this point I've given up on it and resigned to a life of solitude.

Sorry for that tangent. Back to the original question. Why do you think so many people assume you just don't try hard enough when you don't succeed at something? Is it really so hard to accept that many factors in life are deterministic? Things you cannot control and you will not overcome with "hard work"?