This is a gross misrepresentation of the reasoning of people who do not leave comments every single time they correct an ID. Nor does failing to leave comments mean that the IDer is being impolite or disrespectful.
Maybe the user is no longer active. Maybe they aren’t interested in an explanation. Maybe I have already provided explanations multiple times for this user and they show no sign of having learned from this. Or maybe they will recognize why my ID is correct without me telling them.
And if I want to include an explanation, this also means deciding what sort of explanation to provide, in what language, and in how much detail. This requires navigating a host of other social questions (how much knowledge does the user have, can I use technical terminology, will they find my response insulting/patronizing, etc.) and requires mental and emotional energy of a very different sort than the skills required to recognize whether it is this or that species.
So I disagree with your premise that including an explanation is automatically respectful and not including one is disrespectful. This is too simple a dichotomy. Explanations may be rude, or perceived as rude, and lack of explanation is not necessarily a signal that the IDer feels they are too busy and important to take time to write a note.
Consider also: if IDers are not expected to leave an explanation when refining an ID or agreeing with one, why should etiquette demand different behavior when correcting one instead? If observers are not expected to provide explanations of their IDs, why do different rules apply to IDers?
Respect goes both ways. If as an IDer I am supposed to acknowledge that observers put time and effort into their observations and care about what they saw, then it is also reasonable for me to expect observers to respect my time and effort helping them ID their observations – this includes both not making unnecessary extra work for IDers (cropping photos, taking a couple of seconds to think about CV suggestions before using them, paying attention to feedback) and also recognizing that I have to make choices about the most effective/meaningful use of my time. Sometimes this may include explaining corrections. Sometimes it may not.
I agree with you that observers should not be expected to carry the entire responsibility for communication themselves – but neither is this the sole responsibility of IDers. Correcting an ID, with or without an explanation, already communicates information (“I think it is this taxon and not your ID”). Just like a telephone call, both parties have various options along the way about how to proceed (picking up the phone or not, leaving a message or not, etc.). While some choices are going to be more effective than others or better received than others, there is no single rule of etiquette that dictates how either the caller or the recipient must behave at any given point in the conversation.
This has nothing to do with seeing observers as a nuisance or some idea that they have to prove that they have “earned” an explanation.
Sometimes we get overwhelmed and miss notifications. Some users have specific ways that they wish to be contacted because they can’t guarantee that they will manage to respond otherwise. I find that the vast majority of the time when an IDer does not respond to a question, it is not because they are intentionally ignoring me, but because they were away from iNat or simply did not see my comment.