We need them. The skin of our hands just isn't tough enough to pick up a casserole dish straight out of the oven, or to hold onto a hot iron skillet handle. They're easy enough to make, whether you knit, crochet or sew. You can find any number of patters on the internet, most all of them free. Or you can make one up yourself. Any five to six inch square will do. Just make two of them and sew them together with the right sides facing out. Or crochet them together. As long as it's doubled, single thread squares make better dishcloths. However, don't make them too fancy, unless you're going to use them to decorate your kitchen with. I've found that if the potholder is too pretty I don't want to use it for its intended purpose, which will make it all grimy and greasy, eventually.
I've even come up with a simple pattern myself, called a Pot Grabber. It fits over iron skillet handles so you don't even need a potholder. Also, a Lid Grabber, which fits over hot pan lid handles. I'll have to write them out in my pattern blog, if they're not there. And I don't think they are. I put them on Crochetville a long time ago. Still, they're out there, and only take a short time to make. I don't sell my patterns, if I come up with one. They're usually so simple that giving them away is best. I like to share my work, not sell it.
Still, for plain, utilitarian potholders, one of the easiest, quickest and best ones I've found is the diagonal potholder
However, I do change it a bit. I'll work the first part of the round just like any other, sc down the ch and not worry about loops. There will still be an unworked loop to use for the second part. Also, for a smoother texture, crochet through both loops of the scs. When you go to sew it together, I don't use whipstitch. I'll do the first two loops as if I was going to, but then just move to the next sc on the side the thread came out of. I think this stitch has a name, like box stitch or something? Anyway, only going through the loop on the top as you see it, and moving down the same side as your needle comes out gives a better-looking seam. There's a video somewhere showing this. Yes, here it is Video
The next plain potholder is the waffle stitch, or Helena stitch potholder. It's also called the thermal stitch. It's double thick without holding two strands together as well, which is good. A good picture tutorial is right here Helena stitch potholder
Both of these are great for beginners, though the thermal stitch one can be fussy if you don't count your stitches and make sure you didn't miss an end stitch, as that sucker can hide. Otherwise, they make great plain potholders if you need one in a snap. They make great gifts too. Give them to brides, friends, family. They'll use them all the time. I made my daughter a couple of hotpads over a year ago and she uses them all the time. It's a round motif that I got from my mom and I sat down and figured out how to make it. Yes, you need two of them and you simply crochet them together with wrong sides touching. They're great for hotpads or potholders.
In conclusion, any solid square that you know how to make will make a great potholder. Use two strands held together if you don't want to do any sewing, or make two identical squares and sew/crochet them together.
Also, on another note, the double knitting technique of the Hoover baby blanket could also be adapted to a potholder too.