The model is not bad in itself - lots of services use subscriptions (phone, newspaper, water, streaming etc.) Nowadays, software subscription is ubiquitous (think clou services, Adobe, Microsoft), and the older “maintenance” fee model is not really different: companies paid up front for a software license and then a regular fee for “support” and “updates”. Which in many cases did not materialize.
Subscription usually work when you sell the content (like Netflix or newspapers) or service (like Dropbox or iCloud). Or you are a monopolist and you could force your clients to it like Microsoft or Adobe (Actually for big business client the subscription may be better than upfront buying software fee, if they need to hire/fire new workers) . Subscription for the calculator app, even if it support development of new features might be not the best idea.
Insurances, water, and electricity come as a monthly fee. A subscription for a restaurant is not likely to be successful. - iA Writer devs
Also iA devs about when subscription doesn’t work
4.1 Customers don’t understand the work behind the subscription
If you don’t live stream multimedia poetry walking up and down Japan, and you offer pretty much the very same thing month after month, people will feel like you charge rent because you can, not because it costs you money to run your operation. People have to understand, and see, and feel, and experience why they need to pay you constantly.
Not all value is visible: In product-based subscription businesses, as well as the traditional buy-sell paradigm, the value-for-value exchange is clear-cut: pay money, get the product. In the service-based subscription economy, that dynamic isn’t always so simple.” – CBInsights: 7 Surprising Industries Turning To Subscription Business Models
This is impossible. People think making software is not a big deal. After all, a copy of your app costs you nothing! They expect support but don’t think about its cost. They expect that it works on the latest iPhone but don’t think that updating it costs you. That may be unfair, but not everyone is an expert on software development economics.
4.2 Customers feel that they get a bad deal
Renting an apartment will be more expensive over time than buying it, but, short term, renting has a lot of upsides. Compared to buying, renting is easy. Renting is less of a financial risk and you stay flexible to change apartments.
If you buy subscriptions but you feel that you end up paying more for the subscription in a year, than you paid for the full version previously, you feel bad. Subscriptions over a year should be substantially cheaper than your previous full version or your paid competitor’s app.