Why was Luke Perry's signature hairstyle on "Beverly Hills 90210" gone by midway through the third season?

If you watch the series from the very beginning, Dylan's hair starts looking scruffy by sometime during the third season. By the fourth season, he sported that scruffy 'do in the opening credits, as opposed to the first three seasons where his hair was fully intact in the credits. Was that change in his hair supposed to emphasize the Dylan character maturing, as people generally aren't obsessed with their looks as they get older? Keep in mind that Luke Perry's teen heartthrob status simmered down sometime during the fourth season. I'm merely basing this on an interview I read which was described as Luke Perry sitting in a diner (where the interview was conducted) while no one mobbed him (FYI, he was by himself with no bodyguard). According to the interview, it was uncertain if 90210 would be renewed for a sixth season, as the series was no longer in its prime, which seemed to have simultaneously occurred with the disappearance of mobbing fans. Therefore, I'm wondering if the decline in Dylan's hairstyle was symbolic of him and the series no longer being The Beatles, so to speak.