I think the problem with web versions of excel-like apps is the lack of trust when it comes to hosting your private information on the sites that would run them.

Do you really want to have your expense/profit reports, customer lists, etc. hosted on some app?

I don't even use Google spreadsheet because of this sole reason and I don't plan to switch. I would like to switch but yeah, I just don't trust private financial data in the hands of any service provider.