Originally Posted by
bobofclashofclans
They require it because when you are on for 24hours a day, how can you be attacked? Imagine if everyone who had decent loot stayed on 24/7? There would be no loot.
They do this because of the bots that keep the game alive as long as possible. They want you to have a chance to get some loot too.
It is also to prevent shield riding that resulted from TH sniping. It is to guarantee that someone has the ability to raid your base for resources just as you would be able to raid them. You don't accrue PBT while on a shield. Once the shield ends, you begin to accrue. At 3 hours, its a 6min kick/15min vg/6min/15vg and 6min kick. Once the VG starts after the 3rd kick, your PBT is reset. So at most, you will be kicked for 18 minutes if you are online for 3 hours straight. If you voluntarily log off before the 3 hour limit and are away without shield for at least 30 minutes, your PBT will reset.
It isn't perfect and does need some tweaks to make it right for the game.