I think the fact that horse crap is much larger than dog crap should make it more of a reason for them to carry around bags. Stepping in dog crap is an annoyance, but stepping in horse crap is a trip back home to change your trousers.

Horses and I have a hate/hate relationship. I hate them.

Same goes for cats and the local animal laws letting them walk around and crap in others' yards. I live next to a crazy cat lady with 20 cats. Fun times.

I suppose it would be hard to pick up and carry around a bowling ball sized pile of horse crap, but the catch-all thing there looks like a pretty nifty idea. I guess it's probably just convieniance, horse owners probably don't have the means to carry around ten pounds of poop whenever they go somewhere, whereas dog feces is generally far lighter, and there is often far less of it.  
 
Not to say I wouldn't like to see the streets void of horse excrements, but I wouldn't expect one to carry all that around.

It would probably be awkward to stop in the middle of the street to clean up, if you even noticed it.
That and when someone walks a dog it's often with the intent of having it dump out.
I don't know just spitballing.
 
Also, I crossed behind a horse once and it almost murdered me so I don't think I'd clean up even if it was mandatory.

Nappys for horses. Wow! That is one part appropriate and one part idiotic. 
 
Maybe there are laws here to, but i have never seen or heard of a person being fined for a horse crapping in the streets, but dogs on the other hand...

I remember seeing horses with diapers.  There are different types.  Some that attach to the horse themselves and other that work like a catch-all connected to the wagon or cab.  Must be a thing in your town.  I suggest you write your local city council and voice your grievance.

Never understood that either, just watch your step I guess, lol.

Every time i walk through a park or even down a street, i always see signs proclaiming the neccesity of dog owners to carry bags to pick up their mess. This makes sense to me, and as an owner of a few animals i can understand the annoyance emiting from anyone who steps in something they don't want to be stepping in. These signs make sense, and they make the world a slightly less annoying place.
 
But why do horse owners get a free ride? The other day i was walking down the street and narrowly avoided stepping in horse crap, and if i did step in the crap my foot would have sunk up to my ankle in the stuff, but what makes it worse was that it was strategically positioned in the middle of a street pathway. I was almost tempted to look around and see if there were kids hiding nearby with a camera to capture the prank. Then the other day i saw a man being fined for not picking up his dogs mess and thought to myself 'alright, justice at work' but then not an hour later i saw a horse walking down the road and stopping to take a crap right in front of a police car, with two police inside, and then causal trot along. Why are there these double standards? 
 
I think that horse owners should have to carry bags with them as well so when we see a person scooping up dogs mess with a carrier bag we should also see horse riders get off the horse and whip out a big black rubbish bag. In addition, i think that the level of fine should also be meaured on the amount of crap that in deposited. If a dog gets caught then they should get a smaller fine that a horse, and as a test they should use the scraping measurement; can you remove the mess with a piece of cardboard or on grass? or, does this mess require you to actually change your trousers as it looks like you were caught in a filthy watered flood?
 
To makes this more games related i would just like to say that i am glad to see Batman getting positive early reviews. The next few days can not get here soon enough.