Imagine a general advice to socially distance, but then also adding, that if you can't socially distance, wear a mask.

Some percentage of people will see that as socially distancing not being as important. How many people? I don't know. Maybe close to zero. Maybe most of the population. That's an unknown factor.

And there is another factor, how many people ar currently properly socially distancing. If no key is doing it, then sure, tell them to wear masks. If everyone is properly distancing, them may e don't break something that works.

We don't know how big those two factors are, so the best we can do is listen to the countries top scientists in the area, and they currently believe that the effect of modifying the general advice would be very small, but that it might still be done at some point.