There are a couple of instruments that I can think of where this would be very important. One is SpaceDrone from Native Instruments Reaktor 5 player. This is a VST that generates a very complex texture on its own and there is no midi involved. It just starts as soon as you insert it. There are a range of controls on the GUI which do have a major influence as to how it sounds and what it is doing. You could never repeat a performance in a million years. Recording audio directly out of this would be essential.
NewsCool is also a whacky drum machine from the same people. There are images that you can draw and manipulate that have a severe effect on what you hear also. NewsCool can also work without any midi input or midi tracks. It does sync to your host tempo though but it can be very random especially if you manipulate the images while it plays.
I have a few other synths too that do involve random sound generation and recording and playing back the midi data does
not yield the same sound being generated on each pass.
So the idea is to be able to capture these performances and while some of them may be average some of them may also be amazing and if you can record them then you have frozen them for life and you then build on those recordings.
Studio One also has the ability to create tracks and the inputs can be direct from any VST or any buss as well including your main stereo mix. (Apart from all the normal input sources of course) It is an excellent feature and I have used it on a few occasions. It allows you to perform live moves either from the mouse or a control surface and record those movements directly. Faster because you don't have to involve automation. Yes it can cause feedback but you just have to be smart enough not to input monitor on certain occasions and you can avoid it.
It is wrong to put down the idea just because Sonar cannot do it or just because you may be someone who does not need it. For others it may be a revelation. That is why we use other DAW's.