Yes... tries, suffix arrays, sketching, cache oblivious data structures and algorithms, splay trees, persistent data structures, etc. are used in a wide variety of places ranging from compilers to compbio to distributed systems, to give some examples. I know I've written applications for which I wanted to use some of these to get a nice speedup, but in most cases I just never got around to them. Of course you'll find ones that are more obscure too. I'm not sure how to give a more useful answer to such a broad critical comment though...

Tries are useful for IPv4 prefix lookup. Routers that don't have hardware acceleration use them. Indeed, some hardware devices map a s/w trie to analogous h/w structures (some use TCAMs). Also interviews...

Interviews.

So many interviews have a tries question and a recursion question.

This class isn't good interview prep. These are a mix of theoretically interesting and/or practical but somewhat difficult (not intro level) data structures/algorithms.