Some do. I've noticed this at particular hotels and larger office buildings in big cities. It's not exactly common but it is something that some building managers set.
In general I'd assess the reasons down to two possibilities, out both:
- Lack of useful data
Reasoning for laziness is easy enough: the wait for an elevator from any floor to the bottom isn't so great that it actually is cause for concern or significant delay on average. There are always the outliers, but they're the minority.
Data is the bigger reason since most buildings don't have data analysis tools to determine where the best place for the elevator should be, be it the first floor or something else. Buildings with their own underground garages may have more traffic from there than from the ground floor. Certain floors may have more traffic to and from their floor. Without some system contently gauging this, it's impossible to tell which floor the elevator should be on to save users the most time. Furthermore, doing so would be at the cost of the building, both for the hardware and software necessary to mine and analyze the data, and for the electricity and additional maintenance cost of the elevator.
So why not just have all elevators default, say, after 10 minutes of non use to go back to ground level? Again, that's something else that would need to be maintained and handled if anything were damaged.
Ultimately the UX of elevators isn't significantly worse because of this missing feature, though with enough research you could definitely make the case that the 1-3 minute wait could be cut in half (or some figure) which, in just one building, would save some enormous anoint of time pretty year for all employees and this help generate a significant return, making it worthwhile for buildings to charge more and offer the service.
If you so and you're successful, that'd make for an amazing case study!