"Let's build up"

The city today is increasing. In my city of Leeds it seems that there in an increasing number of developments taking place. More to the point, there are all being built taller and taller. Since the introduction to the Darlic (the building by the train station which was listied in the top 10 of worst architecture this year) it seems there has been a trend in Leeds to build taller buildings and more of them.

This is not a rant against the idea but, other than space per square meter is there a reason for it?