Because the "widest" part of the tree is at the top, the base (whether on a stand or hung from the ceiling) takes up minimal floor area.
With the wide branches lifted away from the ground, there is significantly more room underneath for large piles of gifts. Child and Pet Safety
If you have curious toddlers or energetic cats, a traditional tree can be a disaster waiting to happen.
This is why retailers and department stores popularized them in the early 2000s; they could display a festive tree without losing valuable floor space for merchandise.