When three or more players limp and then everyone calls a raise, the raiser has no range advantage and no fold equity on the flop. This is not a c-bet spot.

Why they do it

Multi-way pots at $1/$2 are different. When four people see the flop, someone connected. The c-bet bluff that works heads-up falls apart here because at least one player has a piece of the board and isn't going anywhere. Firing into four players with air is just lighting money on fire.

The adjustment

Check back the flop in multi-way pots unless you actually hit something. Wait for a real hand to build the pot. Aggression works best when there are fewer players to get through.

What it's worth

Firing c-bets into multi-way pots and getting called in two spots is one of the fastest ways to bleed chips at $1/$2. Checking back is free. Use it.