Flex is used in enterprise apps with tables populated with a huge number of columns. Sometimes there are more than 30 columns and there is no way to reformat them by splitting (it may be a strict requirement by enterprise client)
The problem is that it drammatically slows DataGrid down. Adobe knew that problem but I think they didn't count it (and didn't fix) because they suppose that this case is not widely spread. Actually that was the reason why the whole team switched to ExtJS a couple of years ago.
