Why indeed:
There are several different types of these inexpensive motorcycle panniers that you can find online at Amazon etc. Many are much too large and heavy, but a few are small enough for a bicycle and they're actually less expensive than many of the bicycle panniers I was looking at. It did involve some creative fabrication to mount them, but wasn't all that difficult. I've had them for 3 years and while they've served me well, I must admit that they're certainly not for everyone. For the credit card touring and day trips that I do though, they've worked out very well, however for those who are traveling cross country with lots of camping gear etc, they're probably not a great choice. They lock closed so are a little more secure, and since they're made of ABS plastic, they're completely waterproof. The smaller ones on my Trek 520 weigh about the same as the Nashbar Cloth Panniers I used to have, but don't hold quite as much. The larger ones on my Haro 29er, which I use more as my winter / utility bike, hold quite a bit, but are a little (but not 2 or 3 times) heavier. Nevertheless, I've traveled over a lot of mountainous terrain with both bikes and haven't noticed any additional weight when climbing the big hills. In fact, on the Trek, with the more streamlined panniers, I do notice less wind resistance when going downhill or into a stiff headwind. Here's the Haro:
The ABS panniers are vulnerable to getting scratched, but I found when I banged up one of them in a bad fall on my 520, that even the deepest scratches could be fixed pretty easily with a little ABS cement, sandpaper, spray paint and polishing compound. Smaller scratches rub out easily with just polishing compound and car wax. Considering the severity of the fall, and that the damage was only cosmetic, I think their durability, at least in this instance, proved to be much better than I would have expected. A similar fall I had some years back did significant damage to the fabric panniers that I had at the time too, so it doesn't seem to be as much of a differentiator as you might think. Lastly, though it shouldn't be a significant consideration to anyone, I can't tell you how many compliments I've gotten on them. While I was passing a local swimming hole recently, I heard someone shout out to his friend, "Hey look, it's that guy with the cool bike".