Finding people who share almost the same tastes as you is very difficult and rare. It is so rare in fact, that many mistake it for love. Liking the same things is an icebreaker in conversations, it can make or break your case. But some tastes are just not meant to be forced. You cannot force that AMAZING band on your friend, they have to like it on their own. It's sort of like naming a pet. No matter how interesting the names you suggest, the person is going to choose his own favorite name, even if it sounds dull to you.
When you have someone that shares the same tastes, you have someone to talk to. Liking the same unique thing together is even more special. But what happens when anything you can talk about has to be something mutually liked? You're building up someone a lot mentally by projecting so many things onto this one person.
There's a difference between liking the same things, and liking the person. So when someone doesn't like the same thing as you, it's their preference, and the point of preferences is that you don't have to explain them.