Because they're about the best that are widely available in the sub-$200 (tripod and head) range. Very few tripods available for under $100 are all that stable. How well does yours resist flexing under a little pressure? How quickly does it stabilize if you jostle it? How steady is it at your normal working height? Remember, for both tripods and monopods, the more segments there are, the smaller the bottom-most segment will be, thus the least supportive.
For the monopod, how big is your bag? Bear in mind what I said above that the mmore sections it has, the smaller and less rigid the last section will be. A 6' monopod collapsible to under 18" (a pretty big bag) is going to need at least 5 segments. Just remember, though, the head will add some height, and if you're 6' tall, your eye level is a couple of inches below that. Adding in the camera and head depth, you may only need 5 ft. or a bit more of monopod for a 6 footer. You might want to look at the Manfrotto 679B monopod, possibly with the 3229 QR tilt head or the 486RC2 ball head, depending on what you usually shot and which lenses you'll use it with.