There are also many times when there is no real reason to use braid. Ask any pier "fishermen" if they use braid and almost every one will say no. For their reasons, ie casting just off a pier and pulling up heavy fish, ere is no need to pay 20+ dollars for braid.
Mono also is needed for leader purposes and freshwater fishing. It is also cheaper for people who fish in snaggy areas here they have to cut off a lot of line.
There are also compromises, 50pd test gorilla braid fishing line is tough as nails, has no stretch, will cut off anyone's line who is fishing next to you
, and casts fairly ok but not well. Plus for 20 bucks you get 300 yards of it.
But sometimes a quality mono line cannot be beat