The problem is that you spend a lot of time preparing the thing with all the drilling, protective covering , loading explosives and what not and then it comes time to push the button and nobody knows if the ting is going to fall down or not. Plus you have the costs of security. All of that time and money is lost.
At least with a high reach or a crane you are creating debris from day 1 so you can start hauling debris offsite.

I think only in rare instances will implosion actually save you time.