There is no "uncertain marginal effect." The science is in, and it's clear.
https://www.nature.com/articles/d41586-020-02801-8
As for "politically fraught" - people are forced to wear things called clothes literally every day. Some are forced to wear business suits and other eccentric, uncomfortable, and context-specific attire.
People are also forced to wear seatbelts and act in other ways which show responsibility for public health - for example by not smoking in public areas.
The political point here is that masks - which have now been proven to be helpful - are only considered a 'politically fraught act' by people who want to politicise the Covid response.
For people who are rational about this, there is no issue.
For people who are hostile to public rationality, there is.