The deal with H3 and H4...

I'm referring to the (Header 3) and (Header 4) tools in wiki editing and posting. They seem very useless. All either of them do is create new lines that one could create simply by pressing "return" or "enter". It's plain and clear what the purpose of H2 does for instance... 

Hi, I'm a new idea!!!

H3

H4

H4 is still kinda new to me. But I realized, H3 only works (for me) if I highlight desired text, something I tried out right now (lol).

" H4 is still kinda new to me. But I realized, H3 only works (for me) if I highlight desired text, something I tried out right now (lol). "

H2, H3, and H4 are more about organizing information for search engines than anything else.  They tell google what parts of information are important.