I distinguish project-oriented IDEs such as Eclipse and IntelliJ from casual IDEs such as Sublime Text.

If I'm looking at something downloaded from GitHub, I use Sublime Text because the focus is on browsing the source quickly. I don't want to have to create or import a project.

Whereas, if I'm actually developing something, I'll use IntelliJ because then I need all the additional build tools.

I think it's a matter of using the right tool for the right job. Opening something in IntelliJ seems like a lot of effort because of the extra step of creating a project, and hence I choose the easier option: Sublime Text.