I'll stick to the guidelines and assume your message is in good will....

It prevents your spits to reach other's noses and mouths. If all of us wear masks, then no spits flying around = no spread.

From what I understand, it is the size of the droplets. The ones leaving the wearer's mouth are much larger, therefore higher chances of the mask stopping them. The ones that are lingering in the air are smaller, which most face coverings (ie, not proper fitted masks) have lower chances of stopping from entering a wearer's mask.

I get that, but mask usage is not 100% for many reasons. Larger droplets hitting the wearers mask from the outside are also possible for many reasons.

Mask usage is good enough. Even better if every person in the world uses them. Want 100% effectiveness? Then stay at home.

Sorry, I didn't mean that it isn't 100% effective, although that is true too.

I meant that not everyone will wear them. The improvement is still >0 in protecting oneself.