Spam is an issue mainly because there are conspicuous meaty targets to be spammed, not in fragmented environments. And a target is meaty for spammers because that target has gathered, more often unnecessary, critical mass (large scale services, broadcast type news /thought leaders/influencers). Else even a small overhead for sending requests will drive away spammer incentive.
E.g. OS exploits were targeted towards Windows, not so much for so many of those Linux distros.
E.g. OS exploits were targeted towards Windows, not so much for so many of those Linux distros.