The adoption of environmental practices by small and medium-sized enterprises (SMEs) is influenced by multiple social system factors, including market forces, judicial enforcement, and government policies. This paper reviews existing literature on SMEs’ environmental practices, categorizing their motives into market-driven, legal compliance, and government-support mechanisms. Additionally, this study identifies key barriers that hinder sustainability efforts and proposes future research directions. This review highlights that while regulatory enforcement and economic incentives serve as key motivators, social system factors—such as stakeholder expectations, peer influence, and cultural values—play a crucial but often overlooked role in sustainability adoption.