"since the result will be not as performant as what they can do with C" -- This isn't the main reason, but it's also not really true. Paradigm changes don't imply "less performance". To the extent programmers believe, herd-like, "C is fast therefore my program will be fast", they are almost always wrong.
A lot of programmers resist learning anything new, for various reasons, but most charitably because they are never exposed to new ideas or paradigms.
A lot of programmers resist learning anything new, for various reasons, but most charitably because they are never exposed to new ideas or paradigms.