Because you are talking about "shares" not money in funds where most
Americans have their retirement money. It doesn't really matter
whether that is a 401k/IRA, a private pension plan or a
union/government employee plan. A significant part of all of that
money is in equities and it is ultimately the worker's (later
retiree's) money.
The only exception I can think of is the federal government and they
have no real investments at all other than whatever our kids can bear
in taxes.