To all the people saying they find masks uncomfortable or annoying, I'd recommend you take a look around at the different options. There are lots of different masks for sale now, and lots of video tutorials on YouTube showing how to make your own masks, so it's a case of trying different shapes and styles to find the mask that is the best fit for you.
The blue and white one-use masks are very light, but I find they make my face sweat a lot and because they are semi-plasticised there is no way for it to be absorbed or evaporate. Also, there is a cost - in terms of money and the environment. Fabric masks are a bit fiddly to make but you can tailor the size and shape to suit your face, and you can choose how many layers of fabric to use. Apparently 3 layers is best, but can be hard to tolerate due to heat. 1 layer is light but probably not very effective. So, for me, 2 layers is my choice. I've used old cotton pillowcases and clothes for the fabric, and for some I've used cords/shoe laces as ties, while for others I've used 6mm elastic and made ear loops. Today I've been making some masks that are sort of bowl shaped, so they don't sit so tight around the nose area. I haven't worn them yet but am hoping they give a little more breathing space so I don't get as hot. I will report back once I've found which mask is my best choice.
The mask thing is a bit of a drag, but I'm totally on board with wearing them in shops etc, because anything that helps to reduce transmission while we wait for the virus is a valuable tool, IMO. I'm not going to challenge others for not wearing them, or get worked up if people are careless in the way they handle/fiddle with them while out, but I hope that most people will make the effort.