Yeah if your use to just being able to open an NPC/Monster sheet or click on a macro to do attacks, it becomes a pain if you haven't already got that critter available, so you need to do stuff manually. Worse if you need to load a token in first as well.
The more you create the more you have available (at least so long as you can import and export between your games), but from games with a rapid levelling mechanic like D&D/Pathfinder, monsters you've prepared at level 1 aren't much good against a level 5 party, and a useless when they get double figures. Flatter games like CoC, you can keep reusing Cultists, Deep Ones and the like.