Suppose you have a dynamic IP from your ISP. You login to X bookmaker using this IP, place some bets and logout. Then next, someone else you dont know, using the same IP logins to the same bookmaker and places some bets. Can the bookmaker, generally speaking, accuse you of going against their rules, cheating or accuse you of duplicate accounts? What if 2 users, not knowing each other, with the same IP, logged to a popular bookie like bet365 and place some bets?
I am asking this because in my country most ISPs give NAT Shared IPs so one of their client will share a public IP with many others, about 100 people per IP, depending on the ISP though. And to get a real IP that only you use, you need to pay a fee of at least 30e/month and it will be static!
Make bookmakers cash cow machines