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>I've heard racecars don't use them
Sometimes. In circle track racing, it's not uncommon for teams to run with no thermostat, and manually prevent overcooling by taping over portions of the grille. This is done strictly for aerodynamic reasons, so that they can get the maximum cooling with a minimum of airflow.
Source is me, I was involved in a lot of local nascar roundy-round saturday night teams in the late 90's and early 00's. most bomber, modified, and late-model teams were running with no thermostat and lots of tape. It was not uncommon for those guys to run so much tape that the water temps would hover around 220º, thermostat or no. The guys were largely more interested in downforce than they were in engine longevity. Nevertheless, extensive idling for engine warm-up was common on cars not running thermostats.
>spirited drivers use a lower degree thermostat if they don't go with a 'no thermostat' route.
This is also common in racing. The reasoning is largely that you aren't actually trying to regulate the temperature of the coolant itself, what you're trying to regulate is the temperature of the cylinder walls and valve seats.
If you have standard 190º coolant at standard part throttle street conditions, then perhaps temperatures on the other side of the cylinder wall are 400º (number pulled out of my ass). To maintain that same cylinder wall temperature under constant full-throttle operation, it's necessary to regulate the coolant at a lower temperature, which leads us to the 160º thermostats used in many racing engines.
Under normal street-cruising use, this would result in overcooling of the cylinder walls and accelerated engine wear. Under continuous heavy load, however, it just keeps the temperature on the piston-side of the cylinder wall where it would normally be at a cruising load with a street thermostat.
That said, this is all overthought. Lots of endurance racing teams run stock temperature thermostats with zero problems.
