It does relate to your ability to bike in a straight line, but the other danger is that you're not looking at what other people are doing.
Relative to their width people on bikes move a lot more side-to-side than a car does - it's not uncommon to see a person on a bike weaving a couple of feet in either direction as they pedal. If cars did this the lanes would have to be 2-3 times the width of the car on either side to accomodate the movement.
Further, having one hand off the handlebars massively diminishes your ability to react safely and accurately.
Granted, the worst that might happen in a bike-on-bike crash is a broken bone or concussion, but for people who aren't at peak health (or who just get really unlucky) this could be a significant, even life-changing event.
Yeah, it definitely is not for everybody, everywhere, every time :-)
I just wanted to point out that danger depends on lots of things.
Many people on the photos I referenced probably are well on their way to or over the magical 10.000 hours of practice riding a bicycle. Most car drivers, similarly, will have lots of experience driving in traffic with cyclists. Also, if you look closely, you will notice those not on bike paths often are in the middle of a road that is not wide enough for a car to pass them. Cars, in that location, do not go faster than bikes. It also does not look particularly busy there.
Relative to their width people on bikes move a lot more side-to-side than a car does - it's not uncommon to see a person on a bike weaving a couple of feet in either direction as they pedal. If cars did this the lanes would have to be 2-3 times the width of the car on either side to accomodate the movement.
Further, having one hand off the handlebars massively diminishes your ability to react safely and accurately.
Granted, the worst that might happen in a bike-on-bike crash is a broken bone or concussion, but for people who aren't at peak health (or who just get really unlucky) this could be a significant, even life-changing event.