Right now, it is probably because they think a mask is going to stop them from getting this "cold". Blatant stupidity.
Its quite documented now that this contagious virus is a bit more that a simple cold, it has killed 354,000 in the US alone,
1,800,000 around the world
So who here is playing stupid and intellectual dishonest ?
The answer to the posed OP question is fear tainted with ignorance.
Kind like why people gravitate to religoius cults in lot of ways when you think about it.