Operating expenses (OE) and Capital Expenditure (CapEx) are two different things. OE is presented in Income Statement and CapEx is presented on Balance Sheet. CapEx are our Non Current Assets.
You do, however, need capital to cover operational risk as reflected in volatility in operational expenses.
I might also note that capital expenditure may be buried in general operating expenditure in banking, because of the relatively short life of capital equipment.
Yet another consideration is that the book value of physical capital (the product of capital expenditure) is generally only a very small part of banks' total assets.
Operating Expenditures provide benefit for a period less than one year (e.g. utilities), while Capital Expenditures provide benefits for a period more than one year (e.g. building, equipment).