Most modern cars have immobilizers that read the key and won't allow the engine to start if it isn't the correct key. Hyundai/Kia decided not to include these on some of their models to save costs. This was all well and good until it was discovered and spread across the internet. Now everyone knows these cars are easier to steal than others, with no easy way for owners to fix the issue.

It was security through obscurity, which is useless without the obscurity part.

Older cars up into the 90s were much easier to steal since you only needed to break the ignition lock or break the steering lock and touch the right ignition wires together. That's essentially what they're doing with these cars now.