When Google released the new permission system in Android, they blew their one chance to actually make permissions meaningful. The fact that "portscan my network" is one of the Other permissions is testament to how unconcerned with user security and privacy they seem to be as an organization (despite, no doubt, some individual developers who care). I'm pretty close to deciding that my next phone will be dumb and featureless.
But still, I can't see why Gmail should need access to those devices, and far less why it should harass me so aggressively about it when it works fine without them.
Just conjecture, but I feel like there was a sea-change at Google regarding attitudes towards users' privacy, about the time that adblock became widespread and competition started heating up between them and Facebook for ad revenue. They're behaving far less ethically than they did even five years ago.
Their piping of apps' access to things like location through Google Play Services to force you to give them access makes a mockery of the permissions system. I really don't like the way they've been doing things the past few years.
Edit: Gmail complains about lack of access to camera and microphone, not location services. Fixed.