First of all, the substitution of “u” for “you” has nothing to do with grammar, it’s just a shortcut often made by people who are typing on phones. Typing “u” for “you” does not affect the function the word plays in the sentence (grammar), though of course the word choice (diction) will affect the reader’s interpretation of the message.
My students can all shift between formal and informal language when the situation requires it, though they don’t always choose to make the effort. If you are trying to keep up with six different texting conversations, with people who all understand and use common abbreviation, the extra time it takes to type out the full words (and to capitalize and punctuate) is just not worth the penalty you pay (in that each message will take you about 5x longer to type).
More important, the typical person who uses a phone to search the Internet on any topic is going to be young, and therefore less likely to have gone to college to learn the kind of formal language that society sees as a marker of class and education.
But that’s not the only self-selection going on here.
A Googler who chooses to search for “an individual” rather than “u” or “you” or even “a person” is probably thinking of a word that contrasts with “society,” and that will affect the nature if the results being returned.
This is really a question of context.