Subscription software cost can be modeled as a one-time fee: you calculate the net present value of all the payments.
For example, if you plan to use this app for 7 years (which is a reasonable expectation for a piece of software's lifetime) and it costs $2 a month, the net present value is somewhere around $138. That is, if you decide right now to use the app for 7 years, you are costing yourself $138 in today-dollars.
Which is rather a lot.
Of course the subscription does have the benefit that you can cut off your usage at any point, however the people asking for a perpetual irrevocable license are probably not the type who appreciate this capability.
For example, if you plan to use this app for 7 years (which is a reasonable expectation for a piece of software's lifetime) and it costs $2 a month, the net present value is somewhere around $138. That is, if you decide right now to use the app for 7 years, you are costing yourself $138 in today-dollars.
Which is rather a lot.
Of course the subscription does have the benefit that you can cut off your usage at any point, however the people asking for a perpetual irrevocable license are probably not the type who appreciate this capability.