That is true but the interests of 250 people simply outweigh the interest of 1. And most of those single car drivers really could have driven to a GO train station. Most of them drive out of convenience rather than necessity.
There are a few, like delivery or sales people who make multiple trips during the day who do need to drive, but most of the 9 to 5 types that drive could have used transit at least to get downtown.
Geez Fuji, it's more than one car using those roads and they are not all downtown commuters. Even when I worked in one of those TD centres, I had to drive because I had to travel from the office to a client. If it was strictly office, I would park at Old Mill or wherever, and take the TTC, which I didn't mind using.
People are entitled to convenience. Until heavy traffic becomes a nuisance, they won't switch to public transit.