Jokes on you; I love Pidgey
Those too lazy to get up and go play Pokémon GO the way it was intended have turned to third-party software to roam the game and collect monsters, without needing to physically move. Niantic has devised an interesting punishment for those with flagged accounts: replace all rare creatures with common ones such as Pidgeys and Weedles.
Unfortunately this also seems to affect players merely using map trackers and IV stat apps, who were previously flagged alongside the targeted bot accounts. Apparently cheaters have already bypassed this, and Niantic is working on a better solution to target only malicious accounts.