Hmm Thanks.
So sites don’t or cannot collect IP addresses of visitors?
Any and all advertisers on the site can collect IP addresses. There's more tracking than just IP, some requiring cookies can be turned off. Other stuff cannot be turned off. See fingerprinting link above.
Sites do collect IPs and time stamps of visits.
Say all the FBI has a browsing history of a suspect, including times visited, but dont know anything else. They go to the site owners and request IP addresses of visitors and the times they visited. FBI then uses that data against the browsing history it has to find the IP address of the individual they are looking for. Then they go to the ISP that owns the address and find out which customer had that IP at that time.