Is the prime purpose of slot cars to race?
A lot of folk want to run a slot car that looks like a real car. If it does not look like the real thing in miniture then they simply will not buy it.
Folk who time trial, which many of us will do more often than race if only to practice, like to see the beauty of a car in miniture simply rolling at speed around the circuit up to a point beyond which damage could be inflicted in the event of the car coming off. Think about those who purchase the expensive resin cars for example.
The slot car hobby does include all out racers who want nothing but a car that will win, and do not care for the detail.
And then there is the hobbyist who puts the detail before winning.
The simple solution is to run identical cars in a race, and then those who are prepared to make sacrifices may end up winners. However, there may be those who are suffiently skilled to win a race without making the ultimate slot car sacrifice.
I would put the detail first every time, as you can always make a car run better, but you cannot make it more detailed.
If you are aware that a car has weak areas and you are purely in it for racing, then simply use glue to hold it together if it really bothers you!
Moped