safeik sakanah -- why have shuls not reinstated mask mandates?

Per the NYC Dept. of Health:

As New York City enters the holiday season, COVID-19 and other seasonal illnesses are seeing unusually high concurrent spikes. To slow the transmission of these viruses, the New York City Health Commissioner issued a Health Advisory that urges New York City residents to use high-quality masks when indoors and in crowded outdoor settings

The referenced Health Advisory states:

1. Everyone, even if vaccinated and even if they have had COVID-19 or flu before, should wear a mask as follows:

    a. Wear a mask at all times when in an indoor public setting, including inside  stores, offices, lobbies, hallways, elevators, public transportation, schools, child care facilities, and other public shared spaces, and when in a crowded outdoor setting. 

Given the standard set down by certain YU Roshei Yeshiva, i.e. "The Torah absolutely condemns and forbids acting in a way which - under any circumstances [emph mine]- may allow for the death of a Jew," I don't understand why shuls (e.g. Young Israel and the like) which align themselves under the YU umbrella have not brought back mask requirements.  Surely there are elderly, immunocompromised, and others who come to minyan and thereby risk exposure to RSV, Covid, flu, and other illness that can prove life threatening. As R' Meir Twersky wrote elsewhere, "It is self-evident that even if the calculated risk to specific individuals within any given minyan were negligible, this calculation would be entirely immaterial because of the danger posed to the k’lal as a whole by convening minyanim. It is a near-certainty -- if not an absolute certainty -- that amongst the many individuals who will elect to participate in such widespread minyanim, there will be at least a few who will indeed contract this dangerous disease."  

L'shaitaschem, what's the heter to now hold maskless minyanim and create a situation of safeik sakanah?  

Even if one does not want to go as far as cancelling tefilah b'tzibur entirely, surely the slight inconvenience of wearing a mask should not only be recommended, but should be halachically obligatory given the danger?