As TechGnome points out, this is the nature of HTML. The philosophy was that you tell the browser what it is, and the browser will make it look good (not nice!). Good as in well-readable. You should not want just an extra newline somewhere.
Now that doesn’t help you much, does it? Ok. Say you want to make a paragraph and you want to give it a little more space on either side. That is a valid reason. Or you want to give all sections of a certain type (code, or quotes for example) an extra 1 line-height margin. What you would do then is hack your style.css
instead, and put the margin there.
This way your layour will look consistent throughout your blog.
Using css it is possible to tweak it down to the finest level; a style rule would look like this:
`
.entrytext p {
margin-top : 2em;
}
This will give all your paragraphs a little more space.