With all the slang and new words of today (and really, any time period), having a solid foundation of proper language means anyone can understand it, no matter a native speaker or someone resorting to using a translation tool. Sure, when both parties understand a new meaning or more modern phrase, there is not much stumbling in the flow of conversation. But when there is a miscommunication or stumble in the conversation, it can interrupt the whole flow, meaning, focus, and interpretation for either party.
I almost throw my phone against a wall when i see the wrong "you're" or "too." It's like: you learned grammar in first grade! It's not that hard to use it! I have annoyed people in the past when I correct their grammar but I want to know if I'm not the only one.
Years ago, using 'you' instead of 'thou' would be concidered bad. Language over time and it should be accepted. Isn't the fluidity of language what's so interesting about them? I certainly think so and love observing them. Language is to convey information, and if the other person understands what you are saying, it is successful.