Maybe I just don't understand
What do the execs in the big corporations actually do to justify their salaries in the millions?
Business is about knowing how to serve customers repeatably and reliably. The CEO (or whatever) isn't doing the serving, or designing the processes.
So what are they for, in fact?
By the same token
Once a business has generated enough revenue to match what was invested in it, plus a reasonable profit (say) - why do the share holders still matter? Why shouldn't they relinquish their shares to the people who do the actual work?
Well, we know why.
And the bosses are proxies for owners so get similar rewards.