Lets say you use a variable named abcd in your function. And a variable named abcb in a for loop inside the same function. But because reasons you mistakenly use abcd inside that loop and modify the wrong variable, so that your code sometimes doesnt work properly.
It's to prevent mistakes like that.
A similar thing is to use const when the variable is not modified.
Having a company behind software means you can pay to have your bugs fixed. Big distros want that stability for their corporate customers. It's no secret or anything. KDE has sponsors, but doesn't have a direct relationship with a huge contractor like RH. Same reasoning for systemd.
I measured my fridge. You could, in theory. Problem is that the motor in the fridge (and in power tools) is an "induction load", meaning it draws a lot more power in a split second when starting. Inverters have to be built with that in mind, or just stronger (killowats range).
With a bit of patching, yea shingles can probably be 30. Unless air circulation is bad, then 10. I worked on one re-shingling the west side, when the east side looked good as new (10yo roof, iirc). Just some weird airflow on that side (neighbours house maybe).
Systemd hate is about it consuming things, and doing things badly.