Try to install Android Studio (make sure to initialise it!) or Eclipse on your system and tell me where it put its executables. Go and indulge in the horror that your local adb binary can be replaced silently without your knowledge. When most mobile operating systems are designed to isolate components together, we collectively are hindering effective security by allowing these low-hanging fruit on our systems.
Sorry but often I just see countless developers that are not that concerned about security and then ask themselves why are users irresponsible about security.