Why don't more people power-walk? I think it comes down to fear, and embarrassment. The thought that "nobody else is out there doing it, so there must be a reason...what am I missing?"

Truth is there is no reason, not a good one anyway. Just not many people get into power-walking, (or speed-walking, or race-walking, or whatever else you want to call it), but it's great exercise and is easier on your joints than running or jogging. Sure, you might feel a little funny at first (or look a little funny, lets be honest), but why let that stop you if it sounds like fun? Get yourself a buddy (strength in numbers!), avoid busy streets and pathways until you get more comfortable, and most importantly do it for yourself only and don't let what other people think bother you!