In reply to Abhisek Sarkar:
uvm_random_stimulus was from the original AVM and has been removed from the IEEE UVM standard. It was just a simple mechanism for generating random stimulus before sequences were introduces in the OVM.
Push mode is mainly for backward compatibility with older testbench methodologies. But there are cases where back-preassue is needed on one driver to compute stimulus on another driver.
I have never anyone use push mode.