Canadian Politics Today

I think you just described the flats so popular in Montreal that have been around since the early 1900's. Most however are limited to 2-3 units tall, and either single or double wide (ie. 2-6 units in a building). The vast majority of buildings are in a row, but there are also many semi-attached and detached buildings as well. If you wanted to go higher, you would need more infrastructure like elevators, lobbies, and these days parking.

Yeah, I was wondering what the obstacles are.  The way I imagined them is one unit per floor so that you get all the benefits of a house (windows on all sides for example as well as privacy), maybe solariums instead of balconies since they're geared toward families, and elevators and multi-floor parking just like all other condo towers we see. 

So basically, there is nothing holding back the concept structurally, it just comes down to what developers want to do to maximize profit.