Challenge: How Come?

He had two special lady friends with whom he enjoyed spending an evening. Their names were Heidi and Lori. As his enjoyment of an evening with Heidi was in equal measure to his enjoyment of an evening with Lori, Buddy would use `the luck of the draw' to choose which of his friends to see.

In particular, at whatever time tickled his fancy (i.e. at random), he would walk into the St. George subway station, where the platform is between the eastbound and westbound tracks, and he would take the first train that came along.

It would seem that, by choosing in this way, Buddy would have ended up seeing Heidi and Lori on a roughly equal frequency basis, as the trains ran on a fixed schedule and there were just as many eastbound trains as westbound.

It turned out that he saw Lori approximately 9 times out of 10.

How come?