We do it all the time
That's the answer I got when I saw a young couple taking their dog on a trail in Sequoia National Park. I had told them that it was not legal to take dogs on the trails. At first they pretended not to understand, so I told them again.
"Oh, we do it all the time," was the reply.
"Only because you haven't been caught..." I muttered.
There are many reasons not to take pets on the trails--and while most people seem to be concerned about the effects on other hikers, the real problem is with native wildlife. Domestic pets may have parasites and viruses for which wild animals have no resistance or immunity. And while you may be able to control your pet...what happens if you do see a bear, or a bear with cubs?
It's said to see knuckleheads like this abuse the parks. Please don't be one of them.