Because you think its ok to take from others by force to ensure people have the things they need. There are still people that need things, so if you have something of value you dont "need", isnt it ideologically consistent for you to give up those things so that people in need wont be?
In case you're not just trolling at this point:
You sound like the creationists who say things like "if evolution is true, why are there still monkeys?". Regardless of the merits of your position, you've clearly misunderstood where liberals are coming from, and you just as clearly think you haven't. It's not anyone else's job to educate you. Read a book.