IPs aren’t totally useless. Assuming no VPNs are used, at a bare minimum they provide the country that the user logs in from. Depending on the operator, further geographic information may be available, for example doing a whois lookup on my IP address will tell you (accurately) that I’m in Oxford.
How often the IP address changes depends on operator as well, mine can change at any moment but it usually goes years without changing.
Hypothetically, if this new owner operates another service that these admin/moderators use, they could correlate dates and IP addresses to identify their accounts on that other service. Maybe that’s undesirable for some reason. 
Yep, I agree with this.