You're not including the defined contribution retirement plans, which are a vehicle for investment.

N.B. I believe 'pension' ≡ 'defined benefit' is an American English thing, which may the source of the confusion. I, my employer, and my provider refer to my private, defined-contribution plan as a pension.

Nearly 22 million people work for the state, federal, and local governments, nearly 20% of the active workforce.

https://www.bls.gov/oes/current/999001.htm

However less than 2.3% of hourly workers (not total workers, but hourly workers) make minimum wage, yet those that claim a good stock market doesn’t benefit most people would argue fiercely over minimum wage which affects only a tiny fraction of workers. So we should be applauding something that benefits “only” 13% of the workforce (though that 13% number with pensions is misleadingly low as pointed out by other comments.)