"There is no demand"

But only because Linux users don't bother writing letters.

If a lot of people asked the banks for a solution, they would of course consider it.

BlackBerries were never really that large, but still many apps ran on them as well.

EDIT: Also, I'm pretty sure the decision makers at banks do not tend to know Linux exists, so we canno really blame them unless we kindly ask them to provide something we can use.