> Marvel and DC have cited their marks in opposing dozens of superhero-related trademark applications at the USPTO, according to the office's records.
It's not like they haven't been using them, they just knew that at this point they'd have lost if they tried to actually fight it. Most previous groups probably folded immediately under pressure from the giants.
I imagine that the DC legal team were well aware that the trademark was indefensible but figured that the expense of counter suing a well funded industry giant would cause most small players to fold immediately. Their luck ran out in the end but they got a few decades out of it.
It's not like they haven't been using them, they just knew that at this point they'd have lost if they tried to actually fight it. Most previous groups probably folded immediately under pressure from the giants.