Must we thought? I seem to have avoided it so far. It's almost as though I have the choice whether or not to buy it (Still not convinced on the matter as the trials I'm playing with could use quite a bit of polish).
I find it odd to compare this to subscriptions. You can still use the software as long as your device & OS supports it (and you can choose whether or not to upgrade those too btw) which you can't do once you cancel a subscription. Regarding Logic and other Apple software, they can give free updates for so long because people pay them thousands of dollars for a computer to run it on, that's a unique business model not possible to most software companies. And I'm sure Logic will eventually get a paid upgrade for V11 at some point too (though hopefully not too soon!). How long do you expect a relatively small company like Serif to survive if they don't ask for some money every few years?
I do wish they'd offer a cheaper upgrade deal for existing customers, other than just the launch price that is available to everyone. (Also hoping that pump out updates more regularly this time, bugs persisted a way too long in V1, and V2 already needs some fixes).