Do companies still use the Merise method? It seems a bit off to me.

I am learning it at school, but it makes many tables that I think could be merged into one...

Never heard of that one, but I was schooled in doing the third normal form to reduce duplication of data. Never went deep enough in that class to cover the exceptions like orderhistory, caching, storing calculated data vs calculate on the fly etc. was a computer class in what equates to Senior High School. Never covered the normal forms or any database theory in my later studies taking programming classes... kinda funny really when I think about it.

Never heard about it. According to Wikipedia it seems to be common in France, but I have no idea if this is recent information.

Anyway it might be desired to not merge tables (see "database normalization").

The approach is appropriate for data processing applications that use databases and those in real-time or batch. During ten years of use, its influence has spread outside France, and it is now being used in Spain, Switzerland and North America.