That works for something where the events being handled are like "serve a web page" or "compile a C function". It doesn't work for a spreadsheet or word processor or a web browser.
It would be more accurate to say that it doesn't work for some of the allocations in a spreadsheet or word processor app. Which is why you still have the global heap, but the point is that not everything needs to be on the same heap that has the same overall lifetime. That spreadsheet might still be running some algorithm that can do what it needs to do with a local heap.
And that aside, there are still many apps that are more like "serve a web page". Most console apps are like that. Many daemons are, too.
I'm not convinced it even works very well for either of those cases. It's common in many applications to return the result of a computation as an object in memory, like an array or string of arbitrary length or a treelike structure. Without the ability to allocate memory which exists after a function exits, I'm not sure how you'd do that (short of solutions which create arbitrary limits, like writing to a fixed-size buffer).
Well, yes, but I'm trying to be generous to the PoV.
My preferred solution is definitely to use the GC. With some help if you want. You can GC the nursery each time around the event loop. You can create and destroy arenas.
