Hard work isn't generally what gets you wealthy though, that depends more on luck.
I suppose if you're counting the people born into, then yeah, but for the people that actually made the wealth....well very few of them didn't involve a lot of hard work. A few young artists, maybe, but if they were unable to work hard they probably didn't keep that wealth.
Unless I'm forgetting some segment of wealth creation....the lottery winners?, I'm guessing they are a tiny fraction of the total (and don't we often read how many of them are bankrupt 4 years later?). Or are you saying it's not the hard work that got them the wealth, it was the luck? In that case, yes, sorta, but if the vast majority of ways wealth is created involves hard work, we can assume that hard work is an important contributing factor in it. Nobody is saying it's the only thing or that if you do it, wealth will 100% come to you. We're saying without it, it's pretty much guaranteed you WON'T be successful.
Saying to yourself "I'm not going to work hard because it's not a guarantee that I will become wealthy" is not a good idea. On the other hand, it makes life a little bit easier for those that do work hard. Less competition you see.