Because it's sloppy? The game I'm making is a randomized platformer, where I want to be able to not only easily add and organize new tilesets but also mobs, traps, items, etc. Creating dummy layouts or dragging off mobs and then destroying them, etc just seems kludgy to me. When I work on something, I tend to organize it as I want it to be finished as I go. If I have 30 possible mobs, I don't want the event logic running for all of them if I'm only using 10 in a given level.
So here's a question then, if I destroy the last instance of an object in all layouts, does it prevent me from creating a new instance (like in the editor) or does it keep the object definition live? If I can create a dummy layout and then choose my enemies, destroy the others and then repeat the process at the beginning of a new level, that's workable but unwieldy.
Edit: Admittedly I'm new to Construct, so I'm still learning it's ins and outs. Event Groups seems to be the way to keep unwanted event logic from executing for anyone else that's interested.