We (almost) have self-driving cars. Aircraft generally self-drive themselves almost all time now. Why not have self-driving aircraft?
Seems a lot safer for now. Pilot can enter anytime if an emergency of non-standard situation is declared (and verified).
You're not thinking like an attacker... sure, this removes the homicidal co-pilot from the equation, but now you have to worry about the homicidal operators who oversee remote control of the system, not to mention the homicidal engineers/programmers/telecom folks who helped design the system and the homicidal hackers who figure out ways to seize control of it. Those would all be new areas of expertise, too, so you're going to discard the time-hardened crew system we currently use and replace it with a bunch of unknowns; that means flawed designs and fresh incompetence, which means many hard/painful lessons over several decades before aviation safety could return to its current pinnacle.
Basically, commercial aviation has gotten almost as safe as it can get. Make any one aspect safer and you're probably adding more danger than you're taking away. That's not to say we shouldn't try: real engineers and analysts need to study the problems and tackle them, but just about every "internet solution" is naively looking at this one situation without considering the system as a whole.