Why do people leave their town hall out of their walls?

I've always wondered this for a long time. I'm a bit confused on why people do this and how exactly it benefits them.

When I play clash of clans, my goal is to earn the most trophies. Doesn't this mean that I need to have a layout with the town hall inside of the walls? A town hall outside of the walls would give the enemy an easy 1 star during raids. During clan wars, this would also give them an easy 1 star, which I DON'T want.

I'm currently TH7. I'm looking for a good layout that would be the most difficult to raid and earn me the most trophies. Can any of you guys explain why placing a town hall outside of your walls would be beneficial? If you all have any good TH7 layouts that are good that would be gladly appreciated too!

Thanks in advance!

Edit: Thanks for the replies! The website you gave me is also very helpful.

So if I'm in a clan and wanna focus on helping my clan in clan wars, farming would not be ideal I'm guessing.

If you leave out your town hall though, its a free town hall for them right? Couldn't they just go for your resources after they destroy your town hall or do you place your collectors and storages inside your walls too?

Most of us forumers are farmers. This means that we go for loot, and not trophies. Farming helps advance your base a lot more than trophies. We don't care is we get trophies, so we put our town hall in the corner. People just get it, and don't go for our loot, so we get a free 12 hour shield.

It is called Farming
People leave their townhall outside, because they want to get a cheap shield from a one star to protect their resources, rather than getting demolished and loose all of them. Farmers don't care about trophys, they just want to steal as many resources as they can from other villages to upgrade their defense.
For good TH7 bases just search around in the forums or visit http://clashofclansbuilder.com/, and you will find some great bases.

Farming!!!