I could reply with a smart-ass remark to your question, but instead I'll answer it: Some people do not pay attention to what they type most of the time from what it seems or they simply don't care. Possibly both.
I think that it has to do with language and technology. 1. English is a second language for many in this country, therefore, they can easily mix those up and use them in the wrong way. 2. Nowadays, who checks their spelling, grammar and syntax, not many since computers and smartphones do it, however, technology won#039;t correct the way the words are used only the spelling.