Why with spell check so easy do answerer's misspell so many words?

They're apathetic toward their writing.

Where I live, we don't use the American spelling.

So some words I use will be spelt a little differently to some other users here, but the spelling that I use, because of my geographical location, is correct for me. Sorry if this offends.

They're probably too lazy to look up the correct spelling. Also, they may be accustomed to text messaging, which is a highly abbreviated form of communication, which they extend to other writing.

Because you can't make it automatic ("Always check my spelling"), because it comes up with stupid choices for the default - a word with two consonants will always be presented as two words - centor will be shown as

cen tor then

cen-tor and by the third choice

center.

about half the time on long answers it never finishes (or actually, never starts, the arrows spinning without asking about words.)

Because people do not read for fun anymore and the passion for the english language is being lost. also we have so many different slangs. and no real common language anymore.