They can fail to legally compel an ISP for customer info (or the individual paying for the service) because an IP address doesn’t specifically link to one person. At best it links to a router, in a house with a single occupant who pays the ISP. That still doesn’t guarantee the owner is the one who used the network at the time (could share internet with visiting guests, neighbors or be a victim of hacking). Often there are multiple people in the house, or it’s an apartment, or it’s freaking public access. An IP recorded from a file sharing protocol infers diddly squat but judges are not known for being adapt at computer literacy, an IP is sometimes enough for it to proceed.