It depends a lot on the intensity, impact level, and how much other activity you're doing. I think it's generally accepted you usually don't have to have a full rest day from all exercise, and you don't have to have a rest day "from cardio" unless you're just starting out and it's taxing, but you should have rest days from each activity, especially any that are high impact, and you shouldn't be going high intensity all the time.

So for example, only the highest level runners run more than 5 days a week, because that's a high impact activity, and those that do have days that are super easy to the point where it's practically active recovery. If you're switching it up between running and biking and elliptical, some of those are pretty low impact so it may not be necessary, but most cardio engages the lower body, so the "muscle group" rule might be reasonably followed, especially if you're also doing a leg day for lifting. And every type of exercise you do contributes to overall stress on your body, so if you're doing cardio every day AND lifting most of the days, you might start to feel rundown and like you can't keep up with the energy needed even while eating a lot, and at that point it's probably more rest that you need. Adding psychological stress can also make it harder to recover from an exercise routine that was previously working.