In the new sets, Rare Trainers are...well...not even here. And common Trainers are normally ones included in starter decks, like Potion and Switch and stuff. Since most of the Trainers are Supporters, they are uncommon. Some really good regulars are uncommon for the same reason.
I guess it's not weird to me. It's sort of just something I'd expect. I figure that Supporters should be uncommon and other Trainers that are good should be uncommon too. I hated Rare Trainers though...man, was I always mad when I pulled one back in the old days...unless it was a Focus Band. Then I was happy.