It's not just a vanity metric. The reason they choose to pay at a very high percentile of the market reference point is so they rarely have good candidates decline offers. Big Tech wants to be in the position where when they see a good candidate that they want, they get them, and don't need to worry about them going to a competitor. And they can usually afford to make that happen.

And knowing that puts you in an even better negotiating position. I got $150K/year extra in stock (which turned into $300K/year a year later when the stock doubled) with the 5 words "I respectfully decline your offer." If they want you enough, large pools of extra money are available to prevent you from declining or going elsewhere.