There are some things I can't understand

My Social Security question for today: Benefits calculations are based on an average wage earned in your 35 highest wage earning years. That would mean people who make more money are eligible for more Social Security funding. Why is that?

You can't argue that they put more money into the system very successfully, because only the first $90,000 that anyone earns is subject to the Social Security tax. Will someone explain it? Thanks.