The distinction between block and inline elements always seemed strange to me. The whole difference is that a block element takes up the entire width thus forcing a line break before and after the element, and an inline element only takes up as much as the content. Why not just have one type of element- an inline element where you can also apply custom height/width, and use that? You want line breaks? Insert a <br />, or maybe add a special tag in the CSS for that behavior. The way it's now, I don't see it solving any problem, and instead it only forces a property that in my opinion should be decided by a designer.

So why the two types?