It is not embassies' role to provide this service. It is quite reasonable to stop.
Of course people will argue that it was perhaps useful to the people of Beijing, New Delhi, etc. but the real question is what does this have to do with US embassies and the US government?
It is the job of an embassy to provide it's nation with travel advise and recommendations. If the host nation cannot be trusted to provide accurate information about air pollution, then the embassies must do it.
I'd agree that it's not the embassies job to inform the citizens of host nation with the data, but that's practically free, once you are already distributing the info to you own people.
What I don't understand is, if it's that useful, could some other embassies not just do the work? The US normally have fairly well staffed embassies, not just some dude in a suit, but surely the WHO could locate appropriate embassies in almost any nation.
If you really want to bring air quality to the attention of travellers it is of course possible to write "Air pollution can be high" on your country page, no need for real time data (why not also UV, pollens, water quality, then?)
The Danish government actually does write that "Air quality in major cities can be very poor" in their travel recommendations for China, and links to statistics (http://www.aqicn.info/city/beijing/). If that data is any good I don't know, but the US government feels that it need to collect it's own data.
Given the current US administration you kinda have to wonder how long it will take for Elon Musk to suggest replacing the existing network with StarLink, to save on cost of course.
In deciding it’s quite reasonable to stop, is the thinking that “mission creep” = bad, so it justifies stopping something regardless of the big picture benefits? Or do you not consider the benefits significant?
Given a business with many departments, say you notice one department has some mission creep but somehow it’s also increasing profitability for the company overall.
What do you focus on - only mentioning stopping the department mission creep, or first mentioning people should make damn sure the value is preserved as they consider any reorganization?
But that's actually besides the point, which is mission and scope. It is not the job of the US government (or of any foreign governments) to provide air quality data in cities around the world and so I find it reasonable if they decide to stop. That's all.
I feel the reactions are much too strong and emotional, probably because many people here have been riled up by Trump and Musk so now overreact to anything they announce.