
Building a real fence around these common things has a bunch of cost and hassle associated with it. You'd have to make the enclosure larger than the object so that access was not prevented. You'd have to spend a lot more than a portable fence because you have to buy all the wood and nails and concrete and paint or stain that it would take to finish the job. Digging holes for fenceposts are not very fun.
Privacy screens are easy to setup and move around. They can clean up the last touches on your garden to make it yard of the month.