Apple aren't doing this to eliminate malware from their systems. Probably just gearing up to the point where it's impossible to run any application that Apple isn't getting a cut of (or is free).
Realistically, malware only affects a tiny fraction of users, and only a further tiny fraction suffer demonstrable loss from it.
Realistically, malware only affects a tiny fraction of users, and only a further tiny fraction suffer demonstrable loss from it.