I don't understand why it never took of (elsewhere than in France) for relational data modeling. It's a really vast and complex method if you want to apply everything, but most devs here use only the part that make database modeling easy.

I should stress that it's purely for relational data, NoSQL didn't exist when they invented Merise and it would have probably been frown upon ;-) So I guess it's not really interesting in most startups environment were NoSQL seems the norm.