The recommendation here in Sweden, who has a similar infection rate to Denmark, is to use mask in places where the infection rate is high and no general recomme

The recommendation here in Sweden, who has a similar infection rate to Denmark, is to use mask in places where the infection rate is high and no general recommendation for places with low infection rate. The reason for that is basically identical to what you wrote. Studies done in low infection areas give relatively fewer chances for the efficacy of masks to be tested, resulting in inconclusive data. Data from high infection rate areas is more conclusive and thus the recommendation is to use mask there where the data shows a conclusive result.