The bank can repossess a collateral if the contract is broken. That's why it is collateral. However, this is a legal procedure and is not subject to their whims

The bank can repossess a collateral if the contract is broken. That's why it is collateral. However, this is a legal procedure and is not subject to their whims. If they set it as a rent, I'll just go to the guys who give me the same money, but I'll own the device. Renting it means that I have no legal recourse against unreasonable search for example. This is not a house and I don't have any rights written anywhere.