I feel like vouchers are a bit of a shitty response to problems?
My mum had to endure a hotel room that was uninhabitable due to stuck a/c on heating, and the room was 30c even when she slept with the door wide open, which was the only way to prevent it heating up even more. The response is not a room swap, it is ‘speak to a chatbot’.
A voucher is like, you had a shitty experience, please come back so you can have another one. Of course people are less likely to use it. How about no, fuck off, and just find a manager to comp the room.