It is extremely common among Anglo-Americans who are dimly aware that anyone speaks a language other than English. If you carefully look through all threads on this site that contain this error, you will find the Stars and Stripes next to fully half of those who commit the error.
While English as a second language may explain some errors, it falls short of explaining why this error is so prevalent. Another error that is relatively new and appallingly common is the question of who Magnus is "versing" in the next round.
I suspect an absence of reading published books by literate authors that have been through a process by competent proofreaders prior to publication explains the preponderance of errors of this nature. I would just say, an absence of reading, but folks are reading these forums, Facebook, text messages, and many other things where misspelling is the norm.
Sorry but this is my # 1 pet peeve as well (well in the top 3):
Loose = not tight / Lose = not win
I have only seen this error quite often in the last 15 years, hardly ever before that. I wondered why it is surfacing so frequently now, but I wonder if it's from the skit (from a movie, SNL? can't remember) "You're a looooooooooser, ha ha ha".
Any one know why this spelling fail is so prevalent now?
The OP may actually be from Portugal and english may not be the primary language there