I would agree but I think it is a case of risk reduction. Many Joe Publics out there cannot and should not wire a plug. All in all, it's safer to have them snap it into an adaptor!
That Schuko adaptor is quite a clever little beast. I suppose these are popular because, from what Paul says, equipment for sale must be fitted with a 13A UK plug or failing which, a Euro/Schuko plug.
have to agree with Sven. Some of those Europlug-to-BS1363 adapters I've seen have fairly flimsy looking contacts in them, and once installed there's little movement to keep the contacts clean and free from oxidation.
Luckily, they're only used for light loads, but I still don't really like the approach.