I recently had a couple of experiences where we ended up towing someone, and was curious whether anyone else ever carries a tow rope.
1) On day 2 of what should have been a 3 day ride into Snowy River NP (southeastern Australia), I broke a derailleur hanger. We coasted back back down the mountain, then reached a few k's of flat dirt road. Walking wouldn't have been the worst thing, but towing worked great.
2) On a normal cycle tour with about 12 of us, my partner started to get heatstroke on the scorchingly hot final day. We wrapped her up in a wet towel, then got the strongest rider to tow her for more than an hour (at close to 30kph!) on flat, sealed rail trail.
In both cases, I just happened to have a piece of paracord around 3m long. It weighs next to nothing, and was easily strong enough. I didn't anticipate using it this way, but now I'm thinking I'll always bring it for this purpose. A 20km tow is nothing compared to a 20km walk, let alone 50km...
Anyone else? Maybe you should?