If you want to track your visitors for analytical purposes to improve your website traffic and want to use third-party analytics services such as Google Analytics, user consent is a must. If you collect user information without receiving consent prior to the process, you are on your way to breach numerous data privacy regulations around the world and that can lead to serious fines.
Therefore, users should be informed if their data is going to be used for analytical or any other purposes if you want to stay consent with the latest privacy laws, such as the EU General Data Protection Regulation (GDPR). By providing exhaustive privacy and Cookie Policy for your website visitors, you can receive consent from your users based on which consent options work best for them and even Google explains themselves that you should receive consent before using their services.
Google says that if you have enabled the Google Analytics Advertising Features, you have to receive user consent for cookies and explain the about the information you're tracking in your website’s Privacy Policy.