Why do you believe having an assigned IP address which doesn't change for a period of time is a security and/or privacy concern?
One way to possibly be assigned a new IP address is to turn off the modem and connect a different device to the modem. The MAC address of the device connected to the modem is passed to the network. So instead of your wifi router connected to the cable modem, connect your laptop. Turn on the modem and your laptop will possibly cause the modem to be assigned a different IP address because the laptop has a different MAC address than the router. However, even after turning everything off and connecting the router back to the cable modem, it may still be assigned the same IP address.
Because it simply is one. Having a dynamic IP configuration grants users safety and security by obfuscating unique identifiers from outside parties. Having an IP follow a specific user for too long creates the risk of having them be identified and tracked by malicious or otherwise exploitive entities or third parties, such as scammers, DDoS, etc. It's part of the reason why many users will employ VPNs.
In any case, I appreciate your comment.
You could use a VPN service to accomplish your goal.
