A tool like IntelliJ can do deep analysis off-line and in the background and only tell you about the results. This is a good tradeoff between fast feedback and deep analysis.

I don't exactly know which kind of analyses IntelliJ performs but assuming that they are comparable to what ReSharper does they are quite different from what for example Coverity looks for.

Oh yes, they do some static analysis but it's not even close to the level of Coverity, sorry if my initial comment was misleading.

Indeed, those real time checks are currently just a convenience, not anything really essential.

Real-time feedback is a usability concern, not just a convenience. Of course, it is not always possible, and we have to settle for non-real-time feedback, but there are definitely usability costs!