I always carry a camera, sometimes two.
I was told back in the early 70's to NEVER carry a camera in a bag on the bike.
The reason was because of the road shock, the camera will eventually get beat up. The couple were a Husband and Wife Film company in Bennington, VT. They went on to tell me that the edges of the lens elements cant withstand the shock and will develop marks that will eventually ruin the lens. Delicate electronics weren't designed to withstand pot holes, (Go Figure!)
As a result, a Mountainsmith waist pack is what I use for my antique cameras and a small Jannd waist pack when its raining for the GoPro.
Some of my cameras are light enough to not suffer to much with the constant abuse of our New England roads, but sometimes good as well as bad habits are hard to break. Having the cameras on me to absorbe the shock has worked well over time.
Carry a camera with you any way you can and use it a lot. Having to carry it in a bag attached to your frame is better then no camera at all, but think about it, Would you want to be in the bag while someone is riding on these streets?