There's a market, just not sure how big. Business class works mostly because there's a big plane full of people paying for Economy (and maybe Economy Premium) and I suspect a lot of business is upgrades for flyers with a lot of status or mostly using miles. With e-entry (not sure how it will work with ETA now), I haven't waited long in London for immigration in ages.

British Airways business class-only flights from the City airport have been off and on. Don't know their current status. I could afford business but it seems like a poor value relative to other things I could do other than maybe a co-pay with miles trans-Pacific.