They don't have nearly the amount of forms of entertainment and responsibilities humans do. TV, movies, video games, the internet...or real life tasks to perform. Most breeds are built for some sort of job.
Boredom is literally a form of torture.
My border collies didn't have to herd sheep their whole lives, so I had to exhaust them via play. It wasn't always possible...so they'd do weird **** like lick windows and try to herd jumbo jets.
My maltese is on that same level. We can play for an hour...once we are both tired, I stop and he sleeps. 30 minutes later, he's wondering "what the ****, let's play fetch."
I'm like nah, and he sits there with his eyes wide open, bored.
Tough dog bones help a lot.