Masks certainly help prevent someone from spreading it if they have it, but ignoring that wearing a mask is still better than not. If you are wearing a mask you prevent yourself from touching your nose and mouth, and while you can catch it through your eyes the primary route of contraction is still your respiratory system. Masks can also prevent some particulate matter from being inhaled, the better the mask the finer the particulates. If someone sneezes in your face it is always better to be wearing a mask than not. The only thing to keep in mind is that masks don't make you immune, they just mildly lower the risk.
Read the second half of that Surgeon General tweet: "but if healthcare providers can’t get them to care for sick patients, it puts them and our communities at risk!" If masks actually didn't work then they wouldn't need to reserve the for healthcare providers. Instead of telling the truth that there is a shortage of masks and that we should prioritize healthcare workers getting them, the medical and media establishment is lying to lower demand. This is very dangerous and even evil as it will likely result in deaths, as when corona burns through next flu season people will still believe masks don't work and will not take that mitigation effort.
Somebody is bad at maths and it's either me, or #TimPool. If the #coronavirus infection rate is higher than reported because it isn't being tested for, that means its mortality rate is far lower than the 2%. A higher, unreported #COVID19 infection rate makes it less frightening - not more.