Why do some functions.php file contain closing tags and others don't?

Hi,

I regularly find a need to add to or alter functions.php files (often in child theme or via plugins) but i cant find any clarity about the following:

This could seem like an odd question but I am keen to understand it once and for all... why are there sometimes php closing tags and other times these are left out?

I have looked through various functions.php files and I cant see any pattern to why some have closing tags and others don’t.

FrameMarket's functions.php file does contain opening and closing tags ?>

Can you advise please. Should I close <?php if i create a new functions.php in my child theme or does it just not matter???

Many thanks
Chris