Perfection is not easy.
Yes, using the tools makes playing easy ― but we do not just play here.
We attempt to perfect the games to a godly level of precision, which involves handling the game as if it were The Matrix ― observing every slightest detail to gain control over it in ways that the makers never imagined. We search for perfection.
To reach that goal, using the features provided by an emulator is irrelevant, as long as the “world” – the game – is unmodified.
It is a massive undertaking to produce a good tool-assisted movie. Sure, anyone can undo when they make a mistake ― but who can spot the error that causes 0.1 seconds of delay in the movie? Who can spot and abuse bugs in games to do seemingly unearthly maneuvers?
Note: Creating good tool-assisted movies has little to do with playing games well. Only a few players that are skilled in real-time play have the will to create good tool-assisted movies (patience and determination count instead of real-time skills), and only a few players that make good tool-assisted movies are truly skillful in real-time playing (almost always in a different game). Bisqwit, for example, does not do well at Mega Man games, although he is the author of the sensational tool-assisted Mega Man movie.