Noob question: Why are IP lookup services sometimes inaccurate?

Hey everyone, total newbie here trying to understand something about IP lookup.

I've noticed when I try to get a user's IP, sometimes different services give me slightly different locations or even different IPs than what I expect, which is confusing for a simple IP lookup. For example:

# Sample output from two different IP lookup APIs
API 1 Result:
  IP: 192.0.2.1
  Country: US
  City: New York

API 2 Result:
  IP: 192.0.2.1
  Country: US
  City: Boston

Why does this happen? Is there a standard way to ensure better IP lookup accuracy?

Help a brother out please...