I've been forced many times to edit the title to make it clear.
Body previews aren't intended to help you "make your question clear." If content quality was the main concern, we wouldn't need a preview at all - you could get the exact same information just by looking at the plain text. It's all there in the text; you can judge whether it's clear or not just by reading it.
Instead, the reason body previews are useful is markdown formatting. It can be hard to guess what your question will look like just from the plain text, especially if you have minor errors like confusing *italics* and **bold** or thinking that strikethrough uses ~~double tildes~~ instead of <s>tags</s>. Previews help you spot mistakes like that beforehand to make sure your question will look the way you want it to.
Titles don't support markdown - what you see is what you get. Therefore, you don't need to watch out for markdown errors. If you want to know if your title needs editing, you can read it straight from the textbox - no preview needed.