Cause they are messy when they eat!

Hence "eat like a pig" the person is messy or a slob when the eat (crumbs and food everywhere)

Interesting angle, but I'm thinking more in quantities. I've seen messier animals.

Uuuuhhhh.... I dunno.

Maybe it's the whole rooting through the food and grunting that happens... **shrug**

Could it be they are indiscriminate of what they eat?

They're just vastly misunderstood. People took the flopping around in mud [to cool and protect their skin] for being messy. ;)

Uhh, has any driven by a pig farm versus a horse 'farm'?

The smell, oh the smell.

QW beat me to what I was going to say.

Perhaps it has more to do with what pigs eat more than how they eat.
Mmmmmm.... slops!

interesting discussion. Of course to this city girl they both smell! But horses are more beautiful, eat less sloppily &the smell's more tolerable!

Oddy,
Having grown up on a pig farm, I think I can dispel some myths here: First of all, "eats like a pig" is right up there with "sweats like a pig". Pigs don't sweat. They just get hot, and die. Pigs are very messy eaters. When eating ground feed, they grab as much as they can, and then kinda toss it back in their throat as they chew, which of course, sends the feed everywhere. But they are thorough eaters and you won't find a speck of it left once they have finished eating. A pig may not shit where it eats, but won't think twice about eating the corn out of another pig's shit or taking a drink of urine while another pig is peeing. Also, by nature, pigs don't smell, and are quite tidy. But if they are cooped up in a confinement building, there are pits below that hold the liquid waste. Once that fermented waste is sucked out using the "honey wagon" and spread onto an open field, it stinks to high heaven. That is what you smell as you drive by a pig farm.

Poor pigs. So misunderstood.