This might seem odd to you but in truth a lot of us live in a cage, with our daily habits and automatic behaviour we´ve created a cage in which we feel comfortable and protected. But this isn´t about that, this is about people who really live, or at least spend a lot of time, in a real cage. Is this weird? I guess to some people it seems weird, though I must admit that people who spend a lot of time in a cage are a bit extreme. But it´s nothing new in BDSM, to use a cage to take away someones freedom.
Of course there are easier ways to dominate a sub, it doesn´t always include fancy toys or expensive devices. But for those that wish to invest a bit in their hobby, a cage can be a nice addition to your dungeon. With a cage you take away the freedom of your sub, they become completely dependent and they´re at the mercy of their Dom/Domme. Maybe some Doms/Dommes keep cages as decoration, though personally I´d think that would be shame not to use it.
It goes without saying that a cage isn´t for everyone, being in a confined space isn´t something everyone can handle and pushing someone in such a situation can lead to a panic. So make certain that you know what you´re doing before you get in the cage, also as a Dom/Domme don´t force your sub into something that will cause him or her to panic. You might think it´s funny, but if it were you in that situation it would probably be less funny for you.
Some people say that living in a cage changes you. If you´re talking about the hour you spend in it on a daily basis then I can´t take you seriously. But for those that are committed to staying in the cage for months, then I´d say that you might be right. I would like to add to this that it´s not healthy and I wouldn´t recommend it to anyone. Still if you feel like it and you have a Dom/Domme that you trust, then go for it!