*grunch*

Sets want to be played fast. Don't slowplay. Even on a quite ragged board like this. I see a lot of people on pp recently who start raising their sets on the river.
You can be easily outdrawn with a set. That's why you want to raise on the flop. The early stages are where a set earns most. So you do not mind to eliminate some of those 4 opponents. One might successfully chase his backdoor-flush or gutshot straight. You don't want to let these people get away cheaply.

And you never know who is still in the hand to pay you off on the river. All those who missed their draws will fold. Those who hit with the last card will beat you. So you depend on bad players calling with any pair or less.
Therefore the call on the turn is an even bigger sin in my eyes.
So raise flop and raise turn. Sets are not invincible. The Pot is huge. Protect your hand!!!