A website estate is an ever-changing landscape. Good processes to manage new site releases and changes to existing sites are imperative but human limitation and evolving regulation leaves you at the mercy of the last update.
Non-compliance with the regulations could leave you exposed to complaints from website visitors or even a DPA investigation. Your processes need to be clear and documented to effectively handle these. You also need to keep records of audits to show compliance status at any given moment in time.
To monitor changes and maintain compliance across any sizeable website estate manually can be prohibitively expensive.