But many funds with 12b-1 fees don't use them primarily for advertising. Instead, they use the fees to pay brokers. Funds that use B shares don't charge an upfront sales fee, or load. But they're not no-load. The fund borrows money to pay the broker and uses the 12b-1 fee to repay the loan.
Many funds also offer small trailing commissions, which pay the broker for years afterward.
Upfront sales commissions. Funds pay greatly reduced commissions to buy and sell stocks, but they still have to pay them. These are deducted from the fund's share price calculations. All things being equal, funds that trade more pay more, and investors get less. Funds have to distribute their income and capital gains to shareholders at least once a year.