Every program attempts to expand until it has an app store. Those programs which cannot so expand are replaced by ones which can.
Every program attempts to expand until it can read mail. Those programs which cannot so expand are replaced by ones which can.
It really is true. My previous employer had a dream of turning their extremely specific web app into a platform, with an app store and everything. I assume that being a platform means big bucks, idk.
[1] https://en.wikipedia.org/wiki/Jamie_Zawinski#Zawinski.27s_la...
E.g. let's look at Eclipse: It was based purely on AddOns right from the beginning. And still many people want to replace it with other things (probably without AddOns).