IP address changes often for a cellular device, so one person can easily appear different just by moving around.
If you login from work, the IP can represent 1000s of individuals of the internet gateway (users behind NAT).
So you'd have to filter by IP, exclude networks of organizations (not easy) to not unfairly penalize an office worker.
Your point is valid for a home user, but even then, there are multiple people in my home network so its one chance per house? I have a family member who enters these in addition as me.