Why is it better to launch rockets from the equator?

Maybe it is, maybe it isn't. If you want to get into an equatorial orbit you launch from the equator going east because that point is already moving a thousand miles per hour in the direction you have to go. If you want to get into a polar orbit you launch from farther north or south so your launch point is NOT going a thousand miles per hour. If you want to bomb another nation you can launch from anywhere, but you still have to consider which direction and how fast your launch point is moving.