Since ISPs have to use dynamic IP addresses to cope with the IPv4 address shortage, a user's address changes, making it harder to track them over time.
ER, what? The days of dial up modems are long gone squire, everybody is on;lune 24x7 these days, so you need as many IP addresses as there are customers.
There is no logic to using dynamic IP addresses for most ISPs.
Biting the hand that feeds IT
