The Corran ferry is where Lower Loch Linnhe gives way to the upper loch. The ferry is still of course very much running, providing a much quicker route to Morvern than driving all the way round Loch Eil. It also provides a rather long route from Oban to Mull via the Fishnish Ferry but this can avoid congestion on the Oban to Craignure ferry if you have not booked, and it is cheaper.
Because there are not that many interesting anchorages in the loch, I suspect the few boats you do see are either local or on their way to or from the Caledonian Canal. Indeed in mid April I have sailed up and down the loch and seen not one other sail. But it is a grand place with remote mountains to the west and not so remote mountains (with some main road traffic noise and the suburbs of the not-at-all-pretty Fort William) to the east. And of course the Ben looms at the head of the loch (Ben Nevis to the non mountaineers).
So nothing much has changed in the last hundred years since Frank Cowper wrote: "I don't think yachtsmen generally, if cruising in a sailing yacht, will care to go up these lochs, unless for some special reason".