The reason why people with a lot of referrals made money was because they are the ones who grew it, maybe you personally didn't learn from a referral or didn't participated form a referral, but with their help HK became something big, thanks to people who referred many others, it became something that tens of millions of people participated, so I am fine with those people making more money than doing a few simple tasks per day.
I also agree with you that without those people who are actively inviting others and running their own promotional campaign to gain more people who will register under them, they are the reason why the project is as large as it is, and those who they invite will also invite others.
They didn't just spend their time; they also spent resources, which is why their efforts will definitely be rewarded. Most projects also ignore the importance of referrals, which is the reason why they reward influencers hugely.