Because corporate financial education isn't part of the YC curriculum and most small companies don't have CFOs. Large companies and smart individuals keep cash

Because corporate financial education isn't part of the YC curriculum and most small companies don't have CFOs. Large companies and smart individuals keep cash reserves in pass-thru depository products like CDARS which do exactly what you describe. You have a virtual account at Bank A that shows your balance, but the actual money is stored across hundreds or thousands of other banks across the US - each holding less than the FDIC insurance maximum.