Although I agree that it would seem natural to have such a method in a standard container class, I would like to make a couple of observations.

First, there are containers that do have a find() method, std::map, for example (although not on a condition). It could be a wrong impression, but to me this tells something. Perhaps, if I intend to do a search, I might be better off using a different structure (rather than a list) that is more suitable for searching, or maybe a different - more efficient - algorithm (such as binary_search(), if applicable).

Second, if you use a container as a part of your own class, defining a find() method is trivial.

I have no doubt that there are other, more technical reasons for the standard library being the way it is, for example, the idea of separation of algorithms from containers by means of iterators.