I had a colleague at a previous workplace. It was a bank, but both of us were working in IT - everyone was dressing casually, we were not customer facing. Except for this guy - he always wore a suit with a tie, every single day. I asked him once why. His answer was

  I like wearing suits

Those tailored suits are garments made to their exact body shape from the finest fabrics money can buy, I doubt they'll be in much discomfort.

I assume that unlike my suit, their suits are really comfortable.

Also I do think there’s a “serious business guy” vibe they want to convey.

You mean, show up in a hoodie at the inauguration of the President? Even billionaires are not exempt from certain social mores.

Besides, suits, if tailored correctly, are perfectly functional garments, and I'm sure all the billionaires have Savile Row++ bespoke tailors.

Suits can be comfortable

Because they can!

They’re billionaires. They can easily afford comfortable suits.