The most likely answer is that the “crappy” vehicle you are referring to probably doesn't have a Mutant Vehicle license.
There are many categories of vehicles that are permitted to move during the event that aren't mutant vehicles including: Disabled Persons Vehicles, Support vehicles for various art projects, Burning Man staff vehicles, including DPW, official local, state and federal vehicles, Vehicles moving between the Gate and camp. Vehicles that the DMV refused to license but the owners decided that they can ignore the rules and are driving it anyway (this does happen).
Some of the owners of these types of vehicles sometimes make an attempt to mutate their vehicle a little, giving you the impression that it is a rather poor mutant vehicle, so it can be confusing. If it doesn't have a DMV mutant vehicle sticker on the back left, then the DMV hasn't approved it.
There are many categories of vehicles that are permitted to move during the event that aren't mutant vehicles including: Disabled Persons Vehicles, Support vehicles for various art projects, Burning Man staff vehicles, including DPW, official local, state and federal vehicles, Vehicles moving between the Gate and camp. Vehicles that the DMV refused to license but the owners decided that they can ignore the rules and are driving it anyway (this does happen).
Some of the owners of these types of vehicles sometimes make an attempt to mutate their vehicle a little, giving you the impression that it is a rather poor mutant vehicle, so it can be confusing. If it doesn't have a DMV mutant vehicle sticker on the back left, then the DMV hasn't approved it.