Most teams now have the whole team show up in Ensenada before the race to finalize race plans and prep. Then they disburse down the peninsula. Once the northern pit crews are done with the car, many return home leaving the car in the hands of the team members farther south.
Now, if you start in La Paz the same plan would necessitate that the whole team would have to travel to La Paz for the start of the race. This alone is a much larger expense in fuel, not to mention more hotel rooms for a longer period. And then what about the poor guy that breaks his car 200 miles into the race. That is a long azz drive back to the States with his tail between his legs.
I don't foresee it happening any time soon.
Has BITD ever raced Reno to Vegas?