If a cyclist or motorbikist or car driver finds a small pile of poo an offensive obstruction in the road..
What will they think to a horse twirling about at the end of the reins whilst the rider hangs them over his or her arm, unfolds a shovel, unpacks a folding bucket, gathers up the poo, and then tries to get back on the river-dancing unicorn, as an offensive obstruction...
A major reason riders don't have to pick up poo is that it is MORE dangerous to stop, get off, fanny about and get back on.. on the road, and carrying shovels and buckets or bags whilst on horseback also increases the risk of accident.
It is annoying that sometimes, on road surfaces, there are things that make the road more slippery than usual.. ice, poo, rotting leaves, mud...
One thing that often poses a risk to horse riders, particularly on hills, is oil from vehicles making the tarmac slippery to shod horses.
I suggest car drivers should stop and clean up any time their car dribbles oil on the roads... after all at least the car stays put when you park it, put the hazards on, get out and start polishing oil up, and you've got a whole car to put the rubbish in when you're done...