This study introduces an agent-based model to examine the relationship between constrained consumer attention and market concentration levels. The model incorporates aspects of social interaction, reinforcement learning, and bounded rationality from a consumer’s perspective. Our findings indicate that e-commerce market concentration prevails despite the lack of product differentiation among the sellers. Importantly, we observe a negative correlation between consumer attention and market concentration ratio, suggesting that a higher concentration in the market is tied with reduced consumer attention. This correlation holds true across varying market sizes and social connection densities. Our research offers a novel perspective that may enhance traditional market structure theories and provides insights into the evolving patterns of market concentration prevalent in the internet economy.