There has to be a reason for subscription, as in continued incremental value, cloud data storage and sharing, some sort of server backend that incurs monthly cost to run and so on.

Just slapping a subscription to a regular desktop application doesn't make sense.

Also, bundling is not a justification for a subscription, especially if one only cares about a single application. This is similar to the music albums which have already undergone unbundling and no one wants to see a bundling where there is no benefit to the consumer.