the biggest reason for subscriptions is. 1. consumer laws don't protect it. and 2. you can quit your job and don't have to be actually productive and work for a living because your users will just keep on "buying" the product every month indefinitely. and finally 3. subscription basically gives you monopoly in any given area you host it; because the user will usually not look or even have the means to look for options or alternatives once they have already tied a percentage of their monthly income to a company for the software or service they provide - as wallets got spread thinner and thinner until they, now, are entirely swallowed by subscriptions.
the only people arguing in favor of subscriptions are those who don't want to work for a living while still taking advantage of the capitalist system.