Paid for car with cash, but dealership gave only one car key and would not explain the reason. Why would they do this.?

They don’t need to explain and it’s not at all uncommon for used cars to come with just one key.

It was YOUR job to check whether both keys were present BEFORE agreeing to buy the car.

If you cannot yet afford to buy another transponder key and to get the car programmed to recognise it then at least get a dealer or an automotive locksmith to delete all missing keys from the vehicle management system on your car. That will prevent anyone using missing keys from being able to remotely unlock the car and from being able to start it. It won’t stop them from being able to open the car but it will usually mean that they set off the alarm in doing so.

Poor salesmanship and trying to save money. Same as presenting the car to customer w barely any gas. Spare keys often cost around $100 if they’re remote, and they don’t want to shell it out. Question is, where’s the spare that came w the car? You may want to inquire further w a supervisor.

Maybe they only had one key to give you. There's no law that says they MUST provide you with two keys.

If it was a used car, it's because the car came with only one key. You can get as many keys as you want made - at your expense.

Maybe they only had one. Every car I ever bought, I just got one.

because later on he has plans for your car :)

I'm guessing they only had the one. Unless it is part of the sales contract that you will be given two keys, the dealership doesn't owe you a 2nd key.

because they only had one key. no obligation to make you another one. now up to you to go out and have one made

They don't owe you a 2nd key. You are free to have another one made.

Most of the time the dealer only received one key from the previous owner - i.e the previous owner lost the other keys. You can have extra keys made via a locksmith.