Be careful with generalizations.
If somebody decides to tear down their 1952 1500 sq foot house and put up a 4000 sq foot model with no back yard, that's not relevant to a debate on transit, because it's still the same number of houses on the street. Whereas if someone takes their 1912 semi detached house off Roncesvalles, which has been divided into flats for the last five decades, and turns it back into a single family dwelling, now you actually have a decrease in density and it matters to transit. That is actually happening, by the way. If the local strip mall has been redeveloped as condos and townhomes, the suburban density is going up and their roads are filling up, while the density in the old City is falling (except for condo development).
I think young families deciding they can't get along without a huge island kitchen with granite counter tops, and taking out a humungous mortgage to get one, is absurd.... but that's none of our business, and it's irrelevant to transit. Unless you change density, or ridership, or traffic, people can do whatever. Those big homes pay more taxes, after all.
- Paul