Why are low elo players so afraid of dodging?

I just don't understand it.

Dodge: You lose 3 LP You have to wait 5 minutes until you can play again Your mmr doesn't get affected anyhow

Play a game that was already lost in champion select: You lose 13 LP You have to wait 15 minutes (or longer if your team holds you as a hostage) until you can play again Your mmr gets negatively affected