I guess the problem is association with war-time practices of cutting flour with sawdust and other measures to "cheat" on consumers – and generally the feeling

I guess the problem is association with war-time practices of cutting flour with sawdust and other measures to "cheat" on consumers – and generally the feeling of getting cheated. Sugar substitutes are demanded by the public (and usually advertised if present), while this is just yet another additive nobody knew about.