That's like saying you shouldn't ride your bike when it's raining, sometimes you have to make exceptions.

 

Your tires are designed to handle some amount of water (assuming you don't have slicks on). Your tires are not designed to ride on loose dirt. I'm not saying that you will not have to ride across dirt at some time, but you should inherently be cautious when doing so. Gravel and dirt are quick ways to bring a bike down.

I was challenging Chornbe's statement that people should train in the dirt. The couple of times I've had to ride across a dirt parking lot, I've always taken it slow and upright. I don't believe you can train yourself to pull your bike out of a slide on dirt. Everybody's got their opinions.

 

lol And that's why we got different bikes for different applications.