Obviously it's very concerning, because the enforcement threat has to be credible. If you're seeing less and less activity on the part of inspectors out there, that becomes a less and less credible threat.
Similarly—although this has been a consistent problem over time—actual prosecutions, even in the milder form of ticketing as opposed to full-scale prosecution, are still exceedingly rare, so one has to wonder how credible the threat that enforcement action will be taken is. You do see a lot of warnings in some years, particularly in 2017-18, but, again, very few actual prosecutions.