The relevance of examining financial inclusion and electronic payment systems is increasing in the context of economic and digital inequalities, which shape trust, fairness, and the ethical functioning of contemporary financial ecosystems across different institutional environments. However, existing research does not sufficiently explain how these inequalities influence the relationship between digital financial development and actual inclusion outcomes, particularly in terms of participation and equitable access within financial ecosystems. The purpose of this study is to analyse the impact of electronic payment systems, internet accessibility, and economic development on financial inclusion through a comparative perspective of the European Union, Bulgaria, and Kazakhstan. The empirical basis comprises time-series data for the period 2010–2024, obtained from central banks and international financial databases, reflecting the evolution of digital financial services, macroeconomic conditions, and the diffusion of financial access across the analysed economies. The study employs econometric time-series techniques, including the Augmented Dickey–Fuller test for stationarity, correlation analysis, and Granger causality testing, implemented using EViews software. The results reveal a strong positive relationship between financial inclusion and gross domestic product per capita (0.961), as well as between financial inclusion and internet accessibility (0.828), indicating the structural importance of economic and infrastructural factors. In contrast, the relationship between payment system penetration and financial inclusion is weak (–0.017), suggesting that infrastructure alone does not ensure inclusive outcomes. Granger causality results demonstrate only limited short-term effects of digital payment usage on financial inclusion (p = 0.082 for Bulgaria and p = 0.109 for Kazakhstan), while no significant long-term causal relationships are observed. These findings indicate that financial inclusion depends primarily on active participation in digital financial systems rather than mere availability of infrastructure, highlighting the role of behavioural and institutional conditions. The study contributes to understanding how reducing economic and digital inequalities, strengthening trust, and ensuring fair access can support the ethical development of financial ecosystems and inform policy and regulatory practices in diverse economic contexts.