Xeris said:
...but I have little sympathy for those who have no excuse for not being able to speak, pronounce or spell correctly - and that includes my father!
It's not easy to change when one is raised with poor grammar skills or in a family where it is not a priority. It can be learned at a later age *raises hand* but it's trickier to remember it when speaking as opposed to the written word.
Schools didn't encourage it in my time (or correct bad grammar) and I bet they're worse nowadays about that.
Don't look down on those with inferior grammar skills. Help them if they want help, but remember, many people are too busy trying to earn a living and survive to care about not ending sentences with prepositions. Not everyone is middle class with a laptop and intelligent friends.