This comes through the interdisciplinary nature of computational linguistics: CS people know that theories and models are just theories and models, and can be mixed and matched to fit your application purpose better. (People love to have pillow fights over principles in programming language designs and other assorted stuff, but in the end you just choose something from the menu that looks tasty or cook your own using everyone's ideas).

Linguists, on the other hand, are after THE TRUTH (i.e., what actually happens in part of human language understanding), or a good model of it. It's not uncommon in linguistics that people will try and construct The One True Model and look down upon anyone who mixes and matches bits from multiple theories - because, anyways, only the grown-ups are supposed to create new ones, and everyone else is prone to mess it up beyond recognition.

Take together the blissfully ignorant mixing and matching habit from the CS side, and the linguistics habit of having mutually incompatible theories that fight over subscribers, and you get the seemingly incongruous habit of CL people to mix and match theories that are not meant to be mixed and matched.