Once upon a time, I was gainfully employed at a company that stored its tickets as flat files, using a homegrown ticketing system which was a bunch of perl scripts. Said system had the same name as the first name of the actor who played Jack Horner in Boogie Nights. It had all the good features of a text-based system ... simplicity and greppability being the biggest ones.

It eventually got replaced by some JIRA-like monstrosity, I don't remember which. All the text-based goodness was lost. The excuse for the move to a different system was "performance", which was half true. I'm guessing that nobody wanted to go fix it.

The point behind all this rambling is that yes - flat files can be made to work in the way you mention. It just isn't an approach that is cool enough.

If the entire company was just you and me, that'd be very tedious but otherwise fine. But even software companies have non-software people on their staff, who are less likely to know how Git works, but can spot some problems we developer folks can't see. We'd want them to tell us about it, but if we add too many hurdles they won't.