This has to be the biggest mistake of the whole pandemic. Exhalation valves dramatically improve the comfort of masks. A cloth mask might give 50% protection, and a surgical mask about 75%, but even after you double the effects to account for filtering both on exhalation and inhalation, that's still only 75% (1-(1-.5)^2) and 94% (1-(1-.75)^2), which is worse than the 95% you could expect from a correctly fitted N95 mask with exhalation valve.

If you protect yourself then you also protect others, because you can't infect others unless you are infected yourself. This focus on filtering exhaled breath just results in people wearing masks incorrectly to avoid the problems of valveless masks, making the numbers even worse than the previous calculation. It's also much easier to motivate people with self-protection than altruism, especially when the people they're helping often don't reciprocate. We've had more than long enough to solve the production problems by now, so N95 should be the minimum standard.