I have to admit that we run one of those such schemes (not my department, I have nothing to do with it) as there is actually a demand for it from clients who, because of the nature of the sector we work in, contract out 99% of both day to day and major site work and from experience have fallen foul of contractors with poor H&S and wish to take all possible steps to show due diligence.
If the client's demand it, why shouldn't we provide it instead of a 3rd party.
This doesn't change my view of them, namely they should not be taken as a sign of competence, just safe working practice - so your new fire alarm might be in T&E but no-one got electrocuted, fell off a ladder or exposed to asbestos during installation.
I've some good small contractors that do install jobs for me, but are limited in who they can work for by the costs of the various schemes, yet are very competent, whilst some that are contractor approved are dubious to say the least.