Is it just me or are they getting kind of lazy? It seems like most of the trainers we get are reprints. I understand they're cool cards and all, but maybe give us some new effects to work with? BTW, out of 67 trainers in the HS-BW format, 39 are reprints. Thats 58%.
There are certain Trainer card archetypes that are immortal. If something goes out, it WILL be replaced. To my knowledge, Pokeball, Switch & Potion have never been out of the format since they were introduced. Other types of cards get variations. There will always be draw cards. There will always be search cards. There will always be recovery cards. Within those categories, you've got SOME options. However, in order to keep things simple, your options aren't huge. Imagination isn't inexhaustable, and it's often simpler just to use effects you've already done, that people liked.
For instance, Fisherman fills a nice slot. It's two Energy Retrievals, meaning it takes half the deck space for the same effect. To balance that and make it so ER isn't completely obsolete, it's a Supporter. It works well with what we've already got/have gotten since. Yes, it's a card that we've seen before. So? It's harder to come up with a card that does something similar enough to fill the slot but different enough to stand on its own. Making a card that can only be played if you're behind on prizes, have 6 Pokémon in play, and haven't played a Supporter yet that lets you pull out 6 energy from your discard is unnecessarily complicated.
However, if they're too close to another card, they're considered cheap knockoffs. (Think how Cheerleader's Cheer, Oak's Visit, Team Rocket's Trickery, Team Galactic's Mars, and Buck's Training were ALL considered Bill knockoffs, not to mention Mom's Kindness.)
So, sometimes card effects are repeated. If, like Copycat & Fisherman, the name isn't specific to a particular region, they usually keep the name. If, like Celio's Network and Rocket's Admin, it refers to a region/game that isn't the main focus then the name is changed. Take Mom's Kindness. It's basically Bill. BUT, it came out in a time where Diamond & Pearl were the big thing. Bringing in a character from Fire Red or Leaf Green wouldn't make sense. So they used a DP character and gave us a nice, straight draw card. Then, when Heart Gold and Soul Silver came out, Bill was in those games. So, Bill was in that set. Exact same card? Yup. But now after rotating, we've still got a nice, straight draw.
...yeah. Don't knock reprints.