Happens to people all the time.
In fact, the reason Tesla was forced to add the single "ding" and double "ding" method of distinguishing between cruise control (TACC) only mode and full lane-keeping Autopilot was due to some accidents in Asia, and at least one vehicle owner sued because it wasn't clear to them which level of Autopilot was engaged because the old method didn't distinguish between TACC-only and lane-keeping ("Autosteer" in Tesla parlance).
Then there was the big recall in China for the same issue. This was all pretty well publicized.
It's very easy to forget Autosteer lane-keeping was turned off due to a lange change. If one is driving on a mostly straight highway for hours at a time and has to do a single lane change which turns it off, t could be hundreds of yards before one realizes you never turned lane keeping back on. That's especially true especially if you have other vehicles in your household, because almost all of the other ones work that way.
Or, if one is dense traffic, you'll be reminded you forgot to turn AP back on when you veer into another car and Tesla's awful "corrective steering" algorithms don't really do anything. That's why almost every other automaker turns their version of lane-keeping assistance back on after a lange change.
I'm pretty sure that decades of human factors engineering expertise and automotive experience went into the practice used by the other manufacturers, and logically, it just seems to make common sense, honestly.
By your logic, Tesla never needed the big blue steering wheel icon or chimes of any kind or any indication either level of Autopilot is on at all because drivers will just..."remember", right? That doesn't pass the common sense test in my view.
Tesla’s driver-assist system just became safer, with the company adding a chime when Traffic-Aware Cruise Control (TACC) is engaged or disengaged. With the new feature in place, drivers would likely be more aware of their vehicles’ active features at a given time. “You will now receive an audio...
www.teslarati.com
You're in a minority. This site and others is dense with people complaining about them worldwide. Would be interesting to compare the typical routes and situations you typically encounter compared to the legions of people who detest the auto-high-beams and find them constantly turning on and off through certain turns, under overpasses bridges, tunnels, etc.