Why are banks ROA so low?

I'm curious to know, why is it that banks' return on assets, or ROA, tends to be relatively low? Is it due to the nature of the industry, with banks needing to maintain large reserves and face regulatory requirements? Or could it be related to the economic climate, with low interest rates making it difficult for banks to generate high profits from lending activities? Are there any strategies that banks can employ to improve their ROA, or is it simply a reality of the banking sector that they must accept? I'd love to hear your thoughts on this topic.