Automatic queueing systems have been applied in many practical settings to guide customers through a sequence of service stages and achieve efficient queueing. However, our field observations of queueing from a large‐scale physical examination center, which adopts an automatic assignment system with the option of discretionary switching, reveal a relatively high likelihood of queue‐switching requests. That is, many queuers request overriding the algorithm's sequence and ask for a different one, leading to increased total waiting times. Motivated by these observations, this study investigates the behavioral mechanisms behind driving queuers’ switching decisions. Specifically, we examine the roles of two competing mechanisms as the waiting progresses: the motivation to explore a better opportunity (to reduce waiting time) and the consumption of cognitive resources for self‐control to adhere to the assigned queue. Our empirical results reveal a U‐shaped relationship between the examinees’ tendency to switch and the service progress. This U‐shaped relationship steepens when more (vs. less) queuers are ahead of the focal examinee and when the time is (vs. is not) “on an hour” (e.g., 9:00 and 10:00). This study contributes to the behavioral theory of queueing systems through a novel perspective highlighting the competing mechanisms driving individuals’ algorithm aversion behavior (i.e., queue switching) during the progress of multiple services, providing insights into how to design efficient queueing systems.