Why does Grammar Rule?

I will be the first to admit, I do not know every single rule of grammar, but I find I am more comfortable than not, obeying the rules. But really, some of them are silly. Are they really necessary?

Take this one for example:

Compound nouns in which the first part is a single letter can be hyphenated (T-shirt) or written as two words (X ray). X ray is written as two words when used as a noun ("His X ray came back clear"), but should be hyphenated when used as a verb or adjective ("We need to X-ray his ankle;" "He has X-ray vision").

Now, seriously, what difference is it going to make in anyone's world, except for some grammar-fanatic, for that hyphen to be there or not be there? Just how much order in the universe would go askew? I'm all ears for the explanation.

Here's another:

You may end a sentence with a preposition. Just do not use extra prepositions when the meaning is clear without them.

Okay. Since when?

I grew up in the sixties and ending a sentence with a preposition got me a red mark on my paper, so I didn't do it out of fear. And now, I'm phobic about it. So, after all these years of suffering and agitation, someone says it's okay to end a sentence with a preposition. But, not to many. And who decides? Well, la dee freakin' dah.

But here's one of my favorites in Grammar (along with the semi-colon) the Ellipsis:

Use ellipsis marks when omitting a word, phrase, line, paragraph, or more from a quote passage.

Ellipsis. I love this word. I think it originally comes from the Greeks and means to 'fall short'. I use these marks -- which are three little dots that I place just so ... -- when I fall short of thought. I probably drive people crazy with them.

Maybe someday I will go back and fill in all those blanks.

"Grammatici certant et adhuc sub iudice lis est. - Grammarians dispute, and the case is still before the courts."
- Horace