Which would have been a reasonable plot point, considering the American government was testing nuclear bombs left and right in the Nevada desert during the 1950s. So initially, when it was time to get Marty back to 1985, Doc and Marty would go to the desert, attach the laser-time-travel thing to the refrigerator, strap the refrigerator to the truck, instruct Marty to get in the refrigerator, then rig the truck so that it drives straight into a nuclear bomb explosion, where the whole contraption would get propelled through time. If this sounds familiar, it should. The concept was rejiggered for Indiana Jones And The Kingom Of The Crystal Skull.
There were two problems. One: Filming on location in Nevada wasn't in the budget. Two: Creating the effect of a nuclear explosion would cost a million dollars, according to Industrial Light & Magic -- which was money the team didn't have. Oh, and Zemeckis was also noticing that there was a rash of incidents wherein kids would crawl into old-fashioned refrigerators and get stuck inside after they latched shut. Attaching his name to action movie that might inspire more child suffocation deaths AND more nuclear explosions didn't sit well in his stomach. So they compromised by switching the time machine from a thermonuclear refrigerator to a terrible sports car designed by a cocaine trafficker.