I use C. And you are right, in my field there is a tendency to a large degree to re-invent the wheel of data-structures :-). Sometimes justified, but most times not. But mostly because C doesn't usually have well-known, industry-standard libraries for common data-structures. Or even if they do, it's kind of trivial to implement basic data-structures (not saying they will be bug-free!) instead of relying on some random distribution of a library from the Internet.

BTW, most times, the problem is not performance, but tight control of memory usage.