There are multiple reasons for excluding certain IPs, the most common ones are;
A known IP list of fraudulent attacks you had in the past and were able to identify.
A Competitor IP that is likely to click on your ads
A Customer that is seeking revenge.
If you want to exclude said IPs for good, follow these steps:
1. Head over to the Exclusions tab
2. Click on Add IP:
3. Add the IP address you want to be excluded
This will now sync directly to your Google Ads campaigns where this IP address will be permanently excluded meaning they will no longer be able to see any of your paid ads.