If someone knows your IP address, they can find approximately where you live, work, or travel. This makes it easier to bombard you with location-based ads.
In the worst case scenario, if someone has access to the IP address history of your mobile phone, they might track your everyday commutes or habits. Fortunately, such information is difficult to access, unless you are under surveillance by the state authorities or have installed an IP-leaking app.
Moreover, due to different reasons, some websites and services may get blocked for users with particular IP addresses.