They may be obscure apps now, but there was a time not long ago people said the same thing about Windows PC's, that antivirus was not needed. These days does anyone who goes without antivirus on a PC, even if they try to use safe browsing practices, are they seen as having common sense? No, and for good reason.
I do not believe "common sense" is enough to keep anyone safe and believe this thinking comes from the foolish notion that Linux (what Android is built on) can't get malware. ANYTHING can be attacked maliciously, it merely needs enough users to provide incentive for people who wish to do malicious things.
For one thing, what guarantee is there that the list of permissions will always be complete under every circumstance. Would love to know what magic software uses on the Play market to ensure that that can never be bypassed so it can be used in all software.
EDIT: And what might be sent out to some hacker before you reflash? Reflashing does no good if the malware has sent out sensitive data.