There is definitely a use case for single participant simulations, for instance, when testing a driver of a newly developed experimental vehicle. (elearningindustry.com)
In one study, the authors examined single participants in a speed - dating event. (journals.plos.org)
Compared to the singles in the non-romantic condition, single participants who saw the Rom - Com reported significantly less satisfaction with their previous relationship.4 (scienceofrelationships.com)