High-speed rail (HSR) has transformed intercity mobility in China, yet its impacts on ordinary residents remain underexplored. This study adopts a grounded theory approach to conduct cross-case analyses of two city clusters, revealing how HSR acts as both a push and pull factor in shaping mobility decisions and everyday life. Through in-depth interviews, we examine how improved accessibility alters social behaviors, family dynamics, and employment opportunities. Our findings highlight significant variation between short-term and long-term travelers, with HSR simultaneously enhancing freedom of movement and introducing new financial and emotional pressures. Crucially, we argue that HSR functions not only as a transport innovation but also as a form of social infrastructure with broad implications for social sustainability, particularly in reducing regional inequalities. The study contributes to transport scholarship by centering the lived experiences of marginalized travelers and calls for more inclusive, equity-oriented infrastructure planning.