[mvpel]

It doesn't take weeks for a shuttle crew to check out, prep, and don their suits for an EVA, and Mars is a far less hostile environment than low-earth orbit.

[KEVLAR]

The delay is so the batteries can charge. The temps at night are over a hundred degrees below zero. The martian day allows for four hours of full sun to the solar panels. It takes several days worth of charging to get underway.
Keep in mind that the rover is designed to last 90 days and travel about 3/4 of a mile during that time. Additionally the landing site is getting darker daily due to the change in seasons there.