Your parents determine a lot of your trajectory. If they don't make the same investement in their kids as the average for the socioeconomic, you start with a heavy penalty. You can work hard, but you'll have to work twice as hard as everyone else.

If you friends gets permit, cars, fully financed studies but you get thrown out to work straight out of high school what is the probability you would give to be able to accomplish the same things as your friends in a similar timeline. Sure you can work hard and you will get somewhere, but is that somewhere anywhere near what could be possible ? I would argue not.

The left often argues about unfair advantage from famillies having money. In my experience it's not the having money part that is important, its the parent willing to invest it in their children. I know some people who accomplished a lot with poor parents, but they got full support from both gov aids and parents, it generally explains a lot.

Without talking about the genetic lottery, life is unfair and hard work isn't really all that's needed. It can never hurt but at the same time you can work much harder than most and never get as much. Add politics in the mix and anything goes.