This research examines the factors influencing the adoption and utilization of Mobility as a Service (MaaS), particularly focusing on carsharing and micromobility. Our objective was to understand how policy, physical infrastructure, social interactions, and individual attributes shape the use of MaaS. To this end, we conducted a systematic literature review using an adapted socio-ecological model. Our methodology involved a comprehensive search in the Scopus database using keywords related to MaaS and socio-ecological aspects, which yielded 420 relevant articles. These articles were analyzed for their alignment with the socio-ecological model across the specific dimensions of Personal Attributes, Community Interactions, Physical and Infrastructural Aspects, and Governance and Policy, as well as their relevance to MaaS. Key findings indicate that political decisions, including cooperation with public transport, environmental zones, and monetary incentives, significantly impact MaaS adoption. The study highlights the importance of policy in implementing micromobility models. Additionally, physical factors like infrastructure, geographic considerations, and urban design are crucial. Social context elements such as age, gender, education, and income also play a significant role, with higher education and income levels, as well as younger age groups, being more likely to adopt MaaS. Individual factors, including personal preferences and ecological consciousness, are pivotal, with perceived economic benefits being a primary driver for carsharing adoption. In carpooling, beyond the expected impacts of financial incentives, we highlighted the critical role of social norms and peer influences, particularly how visible carpooling by peers can drive adoption rates--a key finding for designing targeted social marketing strategies. For micro-mobility, the crucial finding was that infrastructure adaptations (such as the integration of dedicated lanes) not only support usage but also significantly enhance user safety and satisfaction, suggesting that physical infrastructure investments must be at the forefront of urban planning for effective micromobility integration. In conclusion, this research underscores the complex interplay of policy, physical, social, and individual contexts in MaaS utilization. It advocates for a balanced, context-specific approach to promoting shared MaaS, addressing both user-specific needs and broader transportation policy objectives. The study also suggests future research directions, including the impacts of MaaS on transportation, the role of technology and data, and the socio-economic aspects. [ABSTRACT FROM AUTHOR]