Taxes for this benefit are capped at $8,240 or 6.2% of salary up to $132,900 [1]. The reason taxes are capped is because benefits are capped. My company could pay a bit more in payroll taxes and they wouldn't care, they'd love to hire 5 more experienced and well compensated engineers like me. There's a similar issue on social security wages - let's say I accumulate $5 million in assets at retirement, I'm going to be earning a pretty good amount of income even when not working, so you could reduce my social security (maybe via extra taxes?). People grumble about that money, "it's mine, I paid for it my whole career" - and you did pay for it in taxes. But things like social security also serve as a crucial part of our weaker societal safety net in America. I want it to be there for people that need it.
I probably won't need it in retirement, but most people will. If I do lose all my money, or say I wasn't as lucky in my life and was hurt or not able to accumulate so much wealth, I want it to be there - for me and others.
[1] https://smartasset.com/retirement/social-security-tax-limit