Lots of padwork and lots of free sparrig are both NECESSARY parts of becoming an effective striker for competition. No doubt. But that doesn't mean everything else is useless and should be discarded. Just like traditional boxers don't discard speed bag training because not all effective MMA strikers use speed bag. "Useful" and "necessary" are two different things. Just because it's not necessary doesn't mean it's not useful.
As for Machida, he fights the way he does because of the way he trains. He doesn't strike like a boxer or MT guy as a result of his training not being identical to a boxer or MT guy. And yes, people who train with him who want to fight like him and move like him will train like him. Forms training isn't going to be the dominant focus of the training--that'll be padwork and sparring--but you bet your butt that forms will be part of it. Just like if you learn striking from a boxer, they'll probably have you work a speed bag as part of that training.
(jump to 1:50 if you're impatient)
And Machida's far from the only guy who has used katas as a component (not the dominant component, but a component) of their training while being successful in a full-contact environment. You know Francisco Filho, K-1 legend? Here he is teaching a packed seminar including traditional kihon and kata: