In my view politicians avoided recommending face masks because there was a lack of them. If they would have recommended face masks, and people would have realized that, there would have been an outcry and accusations of failure of the political system.

In addition, the often cited “lack of evidence” of protection from infections for people wearing masks could be a mis-interpretation of a lack of studies examining this question (Absence of evidence is NOT evidence of absence!).

For example, 3 years ago there were also newspaper articles about that there was no evidence supporting the efficacy of using dental floss to improve mouth hygiene, but actually there was just a lack of studies, examining this trivial question. People stopping using dental floss or brushing teeth would have been badly advised …

References:
[1] https://www.theguardian.com/…/dental-floss-proof-works…
[2] https://newsinhealth.nih.gov/2016/11/dont-toss-floss