no they didn't indeed.
alas
but as erendorn pointed out, there are economic factors more complicated then mere "economies of scales" involved in selling a product.
and supply versus demand isn't just a matter of lowering the price (or making buyers willing to pay a higher price) neither.
even though until recently the mere fact of having NOKIA written on it was premium enough to warrant one >¦-)

neither Maemo and not even MeeGo are (or ever were) ready for consumers.
like it or not
NOKIA's management may have been an indecisive bunch but they would have pushed the MIDs out to the masses (just like they did push the 7710) if they had the feeling they were ready.
actually they did, but the mere fact the none of the N900's predecessors had a SIM made them unattractive. not only to consumers but also to providers, as it wasn't possible to milk the customers on their broadband consumption.
i would have bought a 770 (instead of a 7710) and a N8x0 (instead of the N95) if they had had one and i'm sure many of the 9000 series aficionados would have made the step too.
trying to argue that having a MID in one pocket and a dumb phone in the other is the solution is total rubbish; a MID without SIM is useless to ppl minimally on the move
when the N900 came out, i made the step, but many former 9000 fans had switched to other smart phones by then