Let's talk about office. Try to open a spreadsheet with macros on an iPad, of course you can't, even if Microsoft wants to implement it, that would violate the clause that an application shouldn't run third party code. A lot of companies have spreadsheets with macros to do their administration (I don't say that this is good, I only say that in the real world Excel is abused and that is a fact).
Safari doesn't have the same support of Firefox/Chrome. In my country for a couple of sites of some public administration you still need Internet Explorer! Even if the site work on Safari, they are probably not optimized for touchscreens and mostly thought to be used with a keyboard and a mouse.
And all the other applications? How about all the management software that is used in all companies?
Email clients? Too basic compared on the one for PC. Other specific applications? The one on iOS are more basic. Specific kind of software to talk to specific equipment? Doesn't exist.
Support for external USB OTG devices? Practically not existent on iOS.