Try selling English-only software in Europe and you generally won't get very far.
If a company was only able to sell 2.6M copies of their digital software before running to expansion problems... good for them! That's a lot of sales and they probably made a great deal off of those sales. Sure, they can grow to 1B users, but they don't have to. There's no requirement for them to do that other than choosing to expand into those markets, and that's strictly optional. The business model is doing fine, there's no need to adopt a recurring payment system for ongoing maintenance.
And let's be honest, even if they do choose to expand into those other markets, the cost to convert the existing product to work in those markets is most likely less than the money they'll earn from selling in those markets, so... is there really a need for recurring payments to support maintenance? Will one-payment sale structures inherently fail to make the product profitable in a given market?