Considering the historical usage of a revolver, it's not hard to figure out. The revolver went in a bib pocket of an overall, it went into glove box, under a car or tractor seat, in the over-coat pocket, and sometimes (only sometimes) into a holster. A police officer might have carried a revolver his whole life and never fired it, just brandished it, hammered loose nails or noggins with it, and tossed it on the table after work every night.

Making a tool like a revolver more complicated by adding an adjustable sight guarantees that the sight will ALWAYS be out of adjustment.

It's only hobbyists or competitors that needs an adjustable sight on a revolver. Maybe too those who can carry in a fine-tuned holster. Certainly not the average vest-pocket-carry citizen that historically carried it concealed but close at hand, in case of the need for belly to belly contact.

I have at least 10 (probably more like twenty) pocket revolvers and Model 10s and pre-10s, that don't have adjustable sights and that's the way they should be. (IMHO). They never get knocked out of alignment, and I don't them shoot competitively.