Excepting for those people who were raised speaking a different Mother Tongue, I think the problem amounts to either (1) laziness, or (2) a careless attitude about the desire to be understood. Those who truly have a desire to never be misunderstood will be conscientious about spelling and grammar. But, how we can install such thinking eludes me.
Laziness definitely comes into the equation. A great deal of students (even adults today!) have learned somewhere along the way that laziness is okay.
This is an interesting idea. I don't think I'd really thought about this one too much, but I can see what you're saying. After all, if you don't care about being understood, why do you need to bother gaining the skills required?
Thanks for stopping by @thekittygirl.