Any serious company should create and protect its own trademarks. Creation process is done by internal employees or with external design agency. So far so good.

But then there's registration process. Usually a patent and trademark national office won't check if your new suggested trademark looks too similar to already registered trademarks (or they do - if you pay them!). They just care if your submission is correct e.g. all forms included. So one is generally responsible for checking all existing registered trademarks in (national) database.