They have the resources. They don’t care. Same reason it doesn’t work on older versions, they don’t care.

Honestly in this case I don’t blame them. This is a niche little app. It’s great it’s available but it’s not going to drive sales. Spending the time and money to make it work on Windows isn’t going to move enough needles to pay for the development time, QA, and support.

Not having to make it work on older versions of macOS also saves time and money. Everyone upgrades eventually. Just wait them out and the users will be ready one day.