Can't server boost for a month

So, I have a yearly nitro classic subscription, and well, I wanted to boost my server. The problem is, I can only boost it for a year. After checking the cause of that, I got a response from the Discord Support Team, they confirmed that I cannot buy a monthly server boost because my nitro subscription is for a year, and not for a month. So why won't you give both crowds a choice on which type of server boost they want to get? It's not as though it should be hard to separate the payments of the nitro subscription and the boosts, as far as I know.