Yes—generally it’s fine to leave a lens hood on when putting a camera or lens in a bag. If an impact is strong enough to damage the hood, you’d usually also be concerned about the camera or lens itself.

The main downside is bulk: a mounted hood takes up more space and may make packing awkward. That’s why many lens hoods are designed to reverse onto the lens for storage. If your hood doesn’t reverse, removing it and placing it around the lens can save space and add a bit of protection.

So, it’s not inherently dangerous to keep the hood mounted; it’s mostly a convenience and packing-space decision.