The cars are objectively too easy to steal. Kia made several outright stupid design choices and decided not to spend $100 on BoM to use a tried and tested immobilizer that genuinely helps prevent car theft. They also put the key barrel switches in a location very easy to access, rather than deep in the guts of the steering wheel shaft like most manufacturers.
Kia tried to save itself a few bucks by drastically reducing their product's security. The fact that other cars aren't being stolen at nearly the same rate is itself good evidence that the thieves are just opportunists.