It's all because of this guy. Uri Geller is a supposed magician, illusionist, and psychic spoon-bender according to himself, and he's made a lot of money on that premise. Geller claimed that Kadabra was an "evil, occult Pokemon", an unauthorized representation of himself, and sued Nintendo for £60 million (about $83,568,000 at the time of my writing this). Nintendo agreed to stop making Kadabra cards (the last ones made were from the 2002/2003 Skyridge e-Reader set) because of this, and you can't very well evolve an Abra into Alakazam without a Kadabra, can you? They did find ways to circumvent this with item cards allowing you to skip middle evolutions, but no Kadabra cards were produced, and as such not as many Abra and Alakazams were either.
In November 2020, Geller rescinded his demands, and allowed Nintendo to start creating Kadabra cards again. This was obviously quite recently, and they haven't made any new cards since. However, seeing as they're now allowed to, it's probably only a matter of time.
Tl;dr Crazy dude that claims he can bend spoons wanted Nintendo to stop making Nazi representations of him in card form, and raised such a big deal about it that Nintendo agreed to shut him up. Recently he went back on what he said all those years ago, and now Nintendo can create Kadabra cards again, meaning the whole Abra family might be seeing some more cards soon.