My take is because people are largely selfish and ignorant beyond their day to day life. Their favorite politicians/personalities told them masks infringe upon their freedoms and they bought it hook, line, and sinker.
Once someone is convinced they’re right, no amount of evidence or information will sway them. Especially now since they have ready access to any echo chamber of their choice and it’s super easy to filter out dissenting information.
I’m just hearing a bunch of good reasons to switch to metamucil, lentils, and oatmeal.