Of course you don't need them, but......they are nice to have for variety and we are vidiots after all.
I recently pulled out Walk the Weight Off 30 Day set and found I really like it now. Don't know why I haven't used it more. The 30 Minute Strength Interval Walk has been my latest "go to" when I don't want to do a strength workout but know I need to. The 20 Minute Chair Stretch is pretty good too. All the walks are a nice variety.
The 21-Day set is good too. I'm not a fan of the strength workout on this one because it has mainly compound moves which I'm not a fan of but others here say it's their favorite. I love the Stride, Stretch, Relax Walk in this set for a light day....about a 15 minute light walk, about 10 minute nice chair stretch and about 5 minute relax breathing.