Like the comment above pointed out, no obligation to tip doesn't mean it's not poor form not to.
I'm German and I always tip unless the service was really bad. I'm not the only one. [0] Quick Googling confirms this is true in France as well (96% of customers usually tip according to that link) [1].
> 96% of customers usually tip according to that link
Interesting, I almost never tip in France. There's no tip line when you pay by card. You may tip if you want (people may leave a few euros...), but it's certainly not frowned upon not to tip. It probably depends on the context too.
EDIT: your reference [1] says that 96% of French people tip, but only 3% on average (it used to be more but has been declining recently).
I'm German and I always tip unless the service was really bad. I'm not the only one. [0] Quick Googling confirms this is true in France as well (96% of customers usually tip according to that link) [1].
[0] https://www.welt.de/gesundheit/psychologie/article177457710/...
[1] https://www.google.com/amp/s/france3-regions.francetvinfo.fr...