It is unfortunate that the only way to get through the regulatory process is copious $ - but it does work. If this project were better funded, it would likely have gotten through.
There is an entire political party representing something like half the population of the US dedicated to shrinking the regulatory apparatus, including the FDA. That doesn't sound like career security to me.
My perception is that the parent commenter is referring at least partly to "subcriminal" or nearly subcriminal behaviour. There is/was nowhere to "put" this kind of individual when they come from these settings, for a whole host of reasons, ranging from: something like "it's your neighbour's mentally ill kid, you really gonna call the cops for THAT?" to "what cops?".
School shooters and "crazy people acting violently" are probably incredibly rare by comparison. Sub/urban environments probably reduce the impact of the mentally ill on their surrounding neighbours in a whole host of ways, in fact -- in no small part because treatment is much less available in rural areas. (There's more of them in a smaller area and they're more visible and increasingly less criminalized, so people get the idea that poverty and health issues of that variety are modern, urban problems.)
Keywords in the literature around this include "community impact" or "community health", but it's not my area.
I wrote some Python code recently that uses a similar data structure (Futures instead of Promises, without knowing necessarily about the data structure's use in JavaScript). It wasn't really for caching.
I modeled mine on the Django ASGI reference library's server implementation, which uses the data structure for maintaining references to stateful event consumers. Exception handling is done with a pre-scheduled long-running coroutine that looks at the map.
I'm curious about your second point -- why exactly do things get bad with high tail latency? Is it only a weakness of the data structure when used for caching? I'm having trouble picturing that.
There is an entire political party representing something like half the population of the US dedicated to shrinking the regulatory apparatus, including the FDA. That doesn't sound like career security to me.