I disagree. If someone travels regularly for business, always getting to the airport two hours early would waste an hour in each direction. At one trip out and back per week (such as most consultants do), that would be a loss of about a hundred hours per year or more than two weeks productivity. If you never miss a flight, you're spending too much of your life in airports. Baring exceptional circumstances (such as a publicized security threat or obvious bad weather IROPs), I wouldn't fly on any airline that effectively required me to arrive at the airport two hours before the scheduled departure time of my flight, but I've never flown charters or LCCs/ULCCs (nor do I intend to do so). However, most frequent travelers are indeed aware of the risks, know the particular airports they use, and have access to elite or premium cabin lines, as well as being ready to go through airport security quickly.

To me, the term scheduled departure is ambiguous when a flight has been announced as being late. If fact, when a flight delay notification is sent to passengers by the airline, where is the line between a delay and a schedule change (especially if someone doens't know whether the change affects other flights on this route on other days)? I can easily understand someone receiving notice of a flight delay and, in the absence of explicit wording that warns of potential consequences if the passenger doesn't report to the airport (check in counter, bag drop, security, and/or gate) by the deadlines based on the ORIGINALLY scheduled time, assuming that the newly announced time is now the scheduled departure time (which of course is generally different from when the flight actually departs). Even a message reminding one of deadlines in terms of scheduled departure times or departure times could still be interpreted to refer to the new revised departure time that reflects the delay as this is currently when the flight is scheduled to depart.

If someone has never been in this situation and isn't a FT geek, it's reasonable that the words scheduled departure time mean the new revised time that reflects the announced delay. Once a delay has been announced, the flight is no longer scheduled to depart at the original time but at the new later time. Airline terminology doesn't always agree with common usage outside of the industry or common sense understanding of what words mean.

ADDED: It's impractical to suggest that someone, especially someone without high tier elite airline status or access to a special phone number for premium cabin guests, telephone the airline to ask whether it's OK to arrive at the airport later. First of all, the time waiting on hold could easily extend to hours (even without IROPs) and exceed the amount by which the flight is delayed or the time that the passenger should leave to go to the airport, even assuming that one has hours to waste rather than spending the time doing last minute essential tasks such as packing, checking out of a hotel and having the bill corrected, or finishing last minute business meetings or assignments. Secondly, the phone agents are unlikely to reliably give an accurate answer or, in some cases, even to understand the question properly. [The last time I tried to phone an airline to ask whether they had an earlier bag drop deadline for some particular large but nonhub airport, the agent just recited the standard policy without understanding that I was asking about the list of exceptions for particular airports, which I knew existed but the phone agent denied. She also tried to give me the recommended time for nonelites in coach, rather than the deadline information. Calling was a total waste of time.]