I recently investigated the situation at my exchange, which is about 1 Km away from me, in an area that has expanded rapidly in the last couple of decades, including adjacent to the exchange itself.
What they seem to have done is to retain the original exchange-only lines (who would be stuck with no FTTC yet) but at some point in the not too distant past started connecting new lines for nearby expanding estates to a new cabinet, which is located directly outside the exchange, on the public footpath. The usual fibre cabinet has been installed there, too, right outside the exchange so those lucky enough to be connected to it can have FTTC whereas older connections sometimes much further away are still without it.
I can see no obvious reason why Openreach could not in theory install one or more additional cabinets outside the exchange or nearby to take in the direct-connecting lines which, presumably, enter the exchange through relatively few concentrated 'bundles' and not individually.
No obvious reason other than large amounts of cost and disruption, that is. So I think economics may lie at the root of this problem and if Openreach think providing fibre directly to some or all of the affected premises will be cheaper in the long run, that may be their solution - in the fullness of time. I hasten to add that much of this is just guesswork on my part but if it's in the right ballpark, I would not criticize Openreach unduly for prioritising the far greater number of consumers connected to existing cabinets, as they have done.
