>>269122Because they're pronounced the same in their accent (and presumably, all other accents). In a fast conversation, should've sounds the same as "should of", so if they don't usually communicate at length via text, their brain just flips a switch and they automatically default to "should of" because they're thinking phonetically, not grammatically. That's the real tell-tale sign that someone is a native speaker. Same case also applies with they're, their, and there. It's a mixture of someone who hasn't been in school for long, let their typing get rusty, and then not caring, they just phonetically spell out the first thing that comes to mind.
>>269261Not to mention, Japanese has a much smaller group of sounds to draw from compared to English. While English has close approximations for practically all of Japanese phonemes, there is no such case for Japanese.
