Explaining Abra's distrust to humansstyLIShT In the wild, whenever you come across an Abra it always teleports away, that being the only move it knows. This is because Abra is the only kind of wild Pokemon that recognizes that you, a trainer, are trying to cram it into that pokeball.
Alakazam has an IQ of 5000, so Abra is most likely also extremely intelligent. They are very distrustful, or scared, of humans. After being caught, all it tries to do is teleport away, back to safety. When it keeps being thrust into battle and gains enough experience, it acknowledges that it will have no choice but to fight. This is when it evolves into Kadabra. Eventually, like most Pokemon, Kadabra will start to trust it's trainer, and fight for him/her happily.
Now, Kadabra can only be evolved through a trade. This is because, when traded, they are suddenly forced to belong to a new human. Instead of the one it now loves and and trusts, Kadabra is now with a total stranger. Feeling scared and threated, Kadabra evolves into an even more powerful form so that it can protect itself from this human.
If you ask someone their least favorite Pokemon they will most likely say Abra. No seriously, I posted 'who's your least favorite Pokemon' on a Pokemon Facebook fan group and 90% of the responses were Abra. - TwilightKitsune