[Rebelgecko]

Many RFID cards are literally just an ID number, and will happily allow you to copy that number to your own RFID card (look up "blue cloner guns", although they have their own downsides). Basically just security through obscurity. Cards that do fancy crypto stuff exist, but odds are your workplace badge, apartment fob, or hotel room key is the simple kind (because those are cheaper)

[account42]

For a lot of applications someone being able to clone the card is also not that big of a problem. E.g. a hotel will invalidate the code on the card anyway when you check out so it doesn't matter for security whether a past guest has cloned the card.