vim modes in IDEs are often inadequate (if this is not immediately obvious, you probably just don't use vim as fully as possible). The IDEs are often (too) complex in the sense of a hodgepodge of GUI options and menus which are hard to navigate. You often can't put the IDE configuration in a version control system easily. IDEs are often sluggish. The plugin system for vim is superior to most IDEs.

It's not that using an IDE with a vim mode is not a possible viable alternative, but it's a game of trade-offs, as usual.