Why does Boston pronounce their basketball team name wrong?
Do you mean Seltics vs Keltics? I've wondered that, too... I suppose because usually in English, "C" after "E" or "I" is pronounced "S". It grates on me, as well, but I also do't obsess over it, as apparently you do. I think a far more egregious spelling is how people in the UK think the "jail" is spelled "gaol".