The only reason there's high bank concentration is due to stupid liberals and their government regulations, especially the flat tax on banks.

Stupid liberals imposed a flat per-bank tax on each bank in order to reduce progressive taxes that take proportionately more from higher income, in a compromise with stupid conservatives to jump start the economy with reduced taxes.

Banks realized that by concentrating through mergers, they could transform the flat, constant per-bank tax into a regressive, declining tax on increasing income based on fewer, larger banks.

The only thing more stupid than stupid conservatives are stupid liberals who agree with them.