Microservices Architecture (MSA) has emerged as a promising paradigm for building scalable and flexible software systems. While extensive research focuses on MSA's technical aspects, there remains a gap in understanding how practitioners make decisions to adopt and implement MSA in real-world organizational contexts. To address this gap, we conducted an in-depth qualitative study through 30 semi-structured interviews with experienced practitioners in the field. Our investigation unveils the intricate factors driving practitioners' decision-making processes during MSA adoption. We highlight the multifaceted influences of reusability, scalability, extensibility, maintainability, and other factors, shedding light on the motivations behind adopting MSA. Moreover, we delve into key strategies practitioners employ during MSA adoption, emphasizing the importance of the Modulith approach as a bridge between monolithic and MSA Our findings underscore the significance of practitioner experience in shaping MSA adoption decisions.