Wasn’t there very low public awareness of the new rules?

A YouGov poll from March 2019 showed that 76% of the British public were unaware of that age verification is being introduced.  The regulator, as well as all the main adult sites, had plans to educate users in the run-up to the new law coming into force.  Meanwhile consumers are increasingly being age-checked for other online activity and will become more used to it over time.