Orcs delighted in infernal machines, loud explosions, and also senseless destruction. Remember Treebeard saying the cutting of trees for no reason and leaving them to rot is typical orcish mischief.

Respecting authority or leadership was not one of their principal attributes. Small warring Orc tribes may well have held out deep into the fourth age, raiding Men and each other

Many evil inventions were made by Orcs. It is suggested these may include gunpowder (Helm's deep?). Either these things were forgotten and re-invented, or the Orcs must at some point have reached a state of friendship to be able to pass this knowledge on to men. Possibly they even interbred and forgot their origins. This would help account for traits such as senseless vandalism, pointless destruction of nature, rapists and muggers which mark the negative sides of humanity today.