Well, see, sure, from the perspective of a working scientist who potentially wants to use iNat data, an observation of a potted cactus uploaded without an ID and not marked as captive/cultivated is an annoyance and may be felt to be a waste of time that could be better used in other ways. From this perspective, making the observation casual is a quick and efficient solution.
But with respect to the needs and desires of the observer, it is neither a helpful nor a particularly generous response. Typically, people who upload such observations are not doing so because they don’t care about producing valuable data or are too lazy to enter even a broad ID – they are doing so because they don’t understand how iNat works or what its purpose is. They don’t know why it is helpful to enter an ID and they may think that iNat is just an app for sharing photos of “nature” (in the sense of non-human lifeforms) and getting an ID for them. From their perspective, what they are doing is a perfectly legitimate use of iNat.
When someone marks their observation as captive/cultivated without adding an ID or a comment, they will not get any sort of notification and they may not see that the label on their observation has changed from “needs ID” to “casual” or understand what that means. They won’t ask “why” because they don’t know what happened and they may not even know that they can see who marked their observation as casual (and if the observer does ask “why”, as the person marking the observation as casual, you will likewise not get a notification and know to respond unless you either actively subscribe to notifications for that observation or the observer knows enough to tag you).
And once the observation is casual, it is unlikely that they will get much additional feedback on it, because the majority of IDers do not spend much time looking at casual observations. So all the observer will learn from this is that their observation has not gotten any engagement. They may continue uploading observations of potted plants without an ID because they don’t know any better, or they may conclude that iNat is stupid and useless and abandon it entirely.
Whereas if the person looking at the observation takes a few more seconds and leaves a comment explaining why they have done what they did, the observer may be able to learn from this to better understand how to use iNat.
Now, we can discuss whether the onboarding new users is something that should rely on the volunteer activity of other users. (I would certainly like to see better integrated support and tutorials to guide users through what is a fairly complex system.) And of course nobody is required to look at unknowns if they feel their time is better spent elsewhere or they do not have the patience to explain iNat to new users. But if one chooses to do so, I think it is reasonable to at least be aware that the observer might benefit from more feedback than would be provided by the course of action that is quickest for the IDer.
(I’ll add that I don’t think it is particularly helpful to think about IDing as unpaid labor by specialists who selflessly donate their time and expertise without deriving any benefit themselves, any more than observers are unpaid field assistants who are not sufficiently conscientious to provide good, usable data for scientists. Thinking of the observer-IDer relationship merely as a transaction seems guaranteed to lead to frustration and unhappiness on both sides. I think it is more productive to instead think of it as a collaboration that involves sharing knowledge in a community, with all parties benefiting.)