I would wager that autocorrect/predictive text on your phone is to blame for that. It is such an overlooked convenience to a problem we solved decades ago that it is on virtually any smartphone.

Typing in a hurry or you forgot to add one more s in the word 'necessary'? No worries! Keep typing incorrectly and the phone will take care of the proper spelling of the word for you! And it will do so faster than you figuring out the right spelling for the misspelled word. Many of us have probably regressed in our spelling ability to some degree at this point.