Good points. I bought a shovel like that at one time. Never found any real use for it, and I think it broke somehow. Granted it was a cheaper one.

My recommendation as a hiker and backpacker would be to just use a stick. If you're digging a cat hole you only need to go 6-8 inches deep. Same with the leaves for a fire pit. As for the shelter I think you'd find carrying an ultralight tent or tarp to be comparable in weight to a shovel and quite a bit drier and more comfortable than a natural shelter made with dirt.

Some people carry a small trowel like this or this, personally I wouldn't recommend a large/heavy shovel though. Plus you'll get dirt all in your pack.