VPN?
Most VPNs use a specific subset of IP addresses. Many bad actors utilize VPNs to obfuscate the origin of the malicious activity, which kind of poisons the well, so to speak.
Like what I'm using mulvad VPN, a bunch of sites will flag me as potentially suspicious traffic. This is, no doubt, because mulvad VPN is a legit VPN, so bad actors are using it, because they know they can get away with it.