There's a few reasons I can think of (some superficial, some significant):

- Github and git will highlight a missing newline in a diff by default.

- POSIX defines a line as having a newline at the end, so if you don't have a terminating new line you may have one fewer lines than you think you have [1]

- If you ever want to append to a text file/source file programmatically with something like echo "something at the end" >> yourfile.txt then you'll be grateful you had the habit of ending everything with a newline.

- If you use a shell that doesn't automatically add one when you do cat filename you'll end up with your prompt sitting awkwardly at the end of the file.

vim, iirc, defaults to automatically adding a newline to any file without you explicitly asking for it, unless you do set noeol and set binary or, in versions newer than 7.4, set nofixendofline

[1] https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1...

I just ran into an issue with that recently. The Pandas library for Python doesn't consume the last line of a CSV unless it's followed by a new line. I would say I couldn't believe that it actually made inject that newline if it wasn't in the input, but Pandas has enough other oddities that it was pretty easy to believe.

`cat`, for instance, definitely cares.

Do you ever do wc? It cares:

  > echo hello > hello
  > echo -n hello > hellon
  > wc hello hellon
         1       1       6 hello
         0       1       5 hellon
         1       2      11 total

Have you used cat recently? [Edit: scrolled down, looks like several other people already beat me to it. Whoops.]

I think it used to be a requirement (technically) for C and C++, though probably not much any more in practice.

The GreenHills C++ compiler does. It's a niche product, admitted.

Literally cat

breaks some crontabs.