Do only drivers fly-tip?

After Simon Bowkett and I spent a couple of hours delivering our latest newsletter
I cycled home along one of my favourite routes - Hart's Lane.
There's hardly ever any motor-traffic. It's green and pleasant. You always meet other cyclists or walkers. It's friendly. There's even signs of badger activity.

 But then, in the dog-leg for motor-vehicles to turn, near the end of the 'drivable' length of road, I came across these four bags of post-fix concrete: set solid. They had been left too long outside someone's home. Their contents had been wasted, now dumped - without regard to their impact.
 For almost anyone it would have been as quick to drive to Pinhoe's excellent new Pinbrook Road Recycling Centre as to drive to this little-visited back lane.
As building waste, and therefore chargeable, the driver would have paid £2 per bag. That's £8.
What sort of person lets £25 -worth of post-fix concrete go solid in the bags they bought it in, but won't pay a third of that for proper disposal?
And, as I was reported this piece of shabby behaviour to Exeter City Council's Fly-tipping phone line the thought occured that only drivers can fly-tip.
How can walkers or cyclists, who like to use Hart's Lane and other remote or less frequented spots, carry the weight of waste that is fly-tipped?
But drivers' fly-tipped rubbish and rubble affects walkers whose children might pick up something dangerous, dog-owners whose dogs might gash their paws, cyclists whose tyres might be punctured.