A lot of the start and parks could probably strain their equipment and maintain a fast enough speed to stay on the track longer. Most of them own their own team, have one maybe two cars and one engine to last the season, they bring a set of tires left over from the last race and they have maybe two paid crewmembers and a few volunteers that work free and are glad to get in the track. The owner/driver is usually someone that has raced all there life and know of no other way to make a living.
The teams with sponsors that run all the races and try to make the chase and some just want to stay in the top 35 in points put in a fresh engine before every race and have three of four sitting in the trailor. They buy 8 to 12 sets of tires at every race and have probably an average of 17 crew members and enginers. I think a set of tires are now around $1800.00 per set and an engine from $60,000.00 to $100,000.00. If the parkers were not at most races and there were short fields it would look bad for NASCAR so these guys pay the entry fee and qualify. They run just a few laps and make an engine last all season and stretch a set of tires probably three races including qualifying and come in with mechanical problems.
They still have to have a transporter and tractor, travel all over the country and have lodging and some nutrition so the money they get for 40th place is not all profit and if they get caught up in a wreck and tear up there equipment they are out of business until thet get it going again. Cost have gotten ridiculous I think brakes, rotors, disc and pads are maybe $8000.00!
I kind of feel sorry for these guys in a way trying to hold onto a life they love and I guess as long as they get off the track quick and don't cause an accident then no harm done.