Email to Professor-Why?

So you guys are really telling me that in EVERY email chain it goes something like:

Dear Professor

xxxx

Sincerely,
Student


Student,

xxxx

-Professor


Dear Professor,

Follow up.

Sincerely,
Student

And so on? Personally, that just seems so unnecessary. For the first email, sure, absolutely, use “Dear Professor” or whatever. But for subsequent emails in the same chain? Clearly, if the professor wants it that way, but that would (personally) drive me up a wall.

There are days when I go back and forth with my (Professor) advisor/boss in a chain of 30+ emails. Thank the stars we’ve done away with formalities because that would be so tedious.