I'm not sure I understand your logic. Are you counting the number of trips along Jarvis as a whole, i.e. road and street?. If so and you are counting trips along Jarvis to justify the 'reclaiming of streets' you'd lose your argument as most are overwhelmingly by car. If you're only considering the 'sidewalks' of Jarvis then pedestrian trips are 100% already (in theory at least) but would only remain 100% no matter how much sidewalk you add so there is no advantage, and little evidence to suggest that decreasing the road space to increase pedestrian space would draw more pedestrians: Yonge Street or Queen Street have very narrow sidewalks but far more pedestrians than Jarvis or University for example.
I'm all for reclaiming urban spaces for the pedestrian but we have to do it in ways that will accommodate commuters too. They are not the enemy. In this day and age must of us are both commuters and pedestrians, often within the same trip, and are intimately tied to both perspectives. Why would we seek to make enemies of ourselves, or any one part of ourselves? So we come back again, as is so often the case with polarized and political wedge issues, to a knee-jerk reliance on a simplistic solution that is to make an enemy of cars/commuters/roads rather than adequately assessing the needs of people to get around.
At heart though I'm with you in that the answer is not to keep building more roads but to keep expanding mass transit such that someday, and someday soon hopefully, the number of trips along Jarvis may in fact truly tip in favour of pedestrians... at which point it would make sense to rethink the street/road divide of the public realm. In the meantime punishing commuters or those who travel by car seems like a band-aid solution to make us feel better even as the open wound beneath continues to rot and spread.
Again, the car is not the enemy; our lack of commitment to transit funding is.