What are the advantages of napping?

(in The Sims4) Completing a nap provides a 6 hour Energized moodlet, which is one of the longer moodlets available.

it's kinda like a Power Nap when driving, you start to feel tired which impairs judgement and you could black out which is dangerous. you pull over and take a 15 minute power nap, this recover you slightly and you feel better than you did 15 minutes ago.

In terms of the game is much the same, your Sim takes a nap to reduce tiredness (the bed icon) so they don't just drop and fall asleep later on. also i think you don't get triple speed when everyone is asleep but one person is napping which means you wont miss a deadline

another way to reduce tiredness without a bed is to drink coffee however this raises the need to go to the toilet so time is lost at some point having to have your Sim go to the toilet (or urinating on the spot which has it's own disadvantages to time management).