If you want to see how language has changed, look through a 1940s-1950s National Geographic, Life Magazine. Look at the copy in the ads. The vocabulary and reading lever are quite above ad copy today IMO. I think that today, you see a lot  more contractions, slang/buzz words etc. - things are much less formal. Part of it may be the schools and part may be that society, even in the notoriously class conscious UK is perhaps more egalitarian. People travel more, they're exposed to different language variations, and we no longer have only three television networks (in the US), where the news anchors and announcers provided to some degree a national standard that people could emulate. People like the pols who used to pride themselves on courtly, formal language have gone to trying to be 'with it' and converse on the level of the 'common people.'  

I suspect that good writing and speaking skills are less important  to get ahead these days so people don't bother. Most of the people in office wouldn't have a lasted minute with the likes of Lincoln and Douglas or even Roosevelt  People used to care. Now, 'folksy ' seems to be what the public wants.

"Democracy is a pathetic belief in the collective wisdom of individual ignorance." - H. L. Mencken