phones are tricky; it is said spelling and dictionaries became regular in English speaking countries about the same time, not too too long ago.
whatever one thinks good spelling or bad confers on the speaker, misspelled words seldom lead to any great misunderstanding -- those not taking SnC to mean Thomas Sowell quickly found Sowell if they checked -- but they do provide a balcony from which to jeer, for those so inclined.
apart from the obvious legal, military and economic necessities of correct spelling, what desirables are served, if any? spelling is artificial and arbitrary, good or bad proficiency scarcely correlates with anything beyond the mere in/ability, FWIW, to spell.