Firstly , I doubt more than 0.1 % of the general population know these figures exist , let alone use them in deciding their travel habits.
What conclusions can be drawn from average passengers per flight on an individual route ? We have no yield information and no cost information and we don't know what the objectives of the airline or airport are .
An airline may be happy with a middle of the day operated route averaging 25 pax per flight if it iis covering operating costs and make at least some contribution to overheads.At the same time it may not be happy with a route averaging 80 pax per flt ,if that route doesn't cover the cost of owning or leasing an aircraft to operate a peak Service.
Airlines like easyjet , Ryanair, BA use sophisticated models to ensure they don't fly empty seats. This involves adjusting fares to provide the required demand.
In the longer term if the airline is having to junk yields in order to fill the flights , the route won't survive .You can't tell from average loads alone if a route is successful or not. The fact that a route is averaging the same number of pax per flt as the same time last year doesn't mean it's producing the same result.They may have cut average yield 20 % to fill the same number of seats as they did last year.
Similarly routes with the same average loads may have very different results depending on yield , exchange rate , costs.
I am interested in the CAA statistics but to suggest there is some conspiracy to conceal info ,or to suggest the general public should use this figures to police actions is OTT . the airlines and airports make their own commercial decisions based on all the facts and figures they have access to.