Why do so many people speak with overly simplistic english?

Is it just me, or is the english language being watered down by people who do not speak eloquently. It seems as if people do not explain themselves properly and simplify their language by using generic words instead of more descriptive words. So many people seem to talk with a 500 word vocabulary instead of a 30,000 word vocabulary. I am not saying that people should intentionally use big words, or make things overly complex however it is kind of appalling to see people talking in this overly simplistic non descriptive language that is used today. Do you think people are becoming less and less descriptive, or were they always like this? I am not saying we should all be english purists. I have nothing against slangs, but I am indeed bothered by people using words such as "mad" to describe angry, and disrespectfulness to describe their child's bad behavior. I also notice people tend not to use proper names for instance they will say "duck" instead of mallard or call something "gay" instead of saying not cool or uninteresting.