IIRC, my 757 allows the use of Wx radar whilst on the ground.
Certainly there are cases for using radar on the ground - perhaps to see what's inside a giant purple thing in the sky at end of the departure runway on a no-wx airfield. An aid for zero-zero taxi, maybe?
But it is not so nice to paint persons and buildings with high-power focus-beam microwaves while taxiing or parked. Might sort out the discount-price pacemakers real fast, along with some other dramatic negatives.
Wonder if your 757 makes you override something to paint with the radar when on the ground, or if it automatically limits power, inclines the beam, or just doesn't distinguish the case?