We have our own native languages with their own idiosyncrasies and we don't make mistakes like "could of" or "you're/your" in those languages. There's just no excuse for those simple mistakes...
Greek has 5 very common and 1/2 rare spellings for the sound 'i' (as in 'kit'): ι, υ, η, οι, ει /υι,ηι
Imagine if people who can't tell you're/your and write 'could of' had to face this reality... They are lazy ignorant people and the other native speakers need to stop enabling them and making excuses.
<edit>
I'm not actually sure if 'ηι' exists, google is showering me with irrelevant results.. in any case, furthermore, there's
two ways to spell 'e' (as in bed): ε, αι
two ways to spell o: ο,ω
two ways to spell the av/ev sound: αβ/αυ , εβ/ευ
two ways to spell the af/ef sound: αφ/αυ , εφ/ευ
and more. Maybe the difference is that all this crap makes you actually pay some attention to the language if you don't want to embarrass yourself