This is a byproduct of the line being too short. From Bayview/Leslie, Line 1 is close enough that taking Line 4 adds a needless transfer, and likewise is only marginally more useful getting to Don Mills compared to a bus. The distance where the transfer becomes worth it is evidently Don Mills and beyond. The stations before it would likewise benefit more from destinations further away from Yonge, creating trips that didn’t exist before (Bayview-Consumers, Yonge-STC, etc).i already addressed this before i saw your post, but those pockets you describe are the only place they can justify building stations. Line 4 would be more successful as an express line, eliminating the three stations in between Yonge and Don Mills and routing all buses to those major hubs. bus routes already connect to Bayview and Leslie yet they still attract very lower ridership. the station that attracts the highest ridership on Line 4 (Don Mills) is also the station where most buses are frequently routed to, which is not surprising.
Essentially, at a certain distance a subway beats any local transit. But Line 4 is not that length, maybe scratching the surface with Don Mills. It simply does not connect enough people to enough destinations for riders to justify it. I guarantee that if Line 4 were extended east or west, ridership at every stop would grow.
Toronto is lucky to be a system that doesn’t need to look solely at density to determine where transit infrastructure is needed. Our bus routes are much clearer indicators. Their ridership also typically correlates with density.
You also can’t just close stations. Just because there isn’t ridership today, doesn’t mean that once extended they won’t become popular. Line 4 was never intended to be this short; it is unfinished, and it’s ridership reflects that.