Improper Use of Apostrophe

Why in God's name do people now feel it's necessary to apostrophize EVERYthing? I see things like "Get great deal's HERE" and "Christmas Tree's for Sale!"
Didn't you get past 8th grade English? And what about things like "did'nt," and "It has it's own charm"? For heaven's sake people - when it's more than one thing, you don't use an apostrophe. When it's two words made into one, you do. Like "it's," the way I just used it. The apostrophe stands for the missing i in "it is." And when you're (you are, not your, thank you) talking about a thing having its own gifts, you don't put an apostrophe in there - it's possessive, it means it belongs to IT. If you put the apostrophe, it means it IS something.
Get it right, you people!