The decision not to wear a mask has, for some, become a rebellion against what they regard as an incursion on their personal liberties. For many others, the choice is a casual one more about convenience than politics. The choice can also be a reflection of vanity, or of not understanding when or where to wear one. Some people said they found masks uncomfortable, and thus a nuisance they were unwilling to tolerate. Others were skeptical how much difference they made outside on a sunny day…

Even as governors imposed orders and public health experts dispensed their professional guidance, the effort to thwart the coronavirus nevertheless amounted to a grand national experiment in cooperation that hinged on the individual decisions of millions.

Gov. Mike DeWine of Ohio had included a face-covering mandate as part of plans to reopen businesses, but he changed course. “It became clear to me that that was just a bridge too far,” Mr. DeWine, a Republican, said Sunday on ABC’s “This Week.” “People were not going to accept the government telling them what to do.”