I do take your point (and I did say pro/semi-pro). Perhaps I see it slightly differently, maybe even rose-tinted (possibly as bad as IR-filtered!?
) but there have to be cost-constraints in producing budget-price cameras and one of the areas where the D40, for example, saves cost-weight is the absence of a lens motordrive in the body.
I think the D40 is targeted at the "new-daddy" consumer that isn't interested in old kit at all. They want (and get) a very capable camera with a really good kit lens and a range of relatively inexpensive other new lenses to pick from, that they can use without having to apply grey matter.
I do think the consumer that's looking for the ability to use a more full range of older glass is probably at the D90 end of the consumer spectrum, where I think they're handsomely catered for.