I like the ease of it, working in the round and without a specific pattern (like almost everything I do!) They are so quick and easy, you can do one in a few hours.
The colours and textures and opportunity to add them to my mostly gray wardrobe. With our chilly winters they are really necessities as well as accessories!
The variety. There are so many style and pattern choices to choose from! I have never found many hats in stores that I have loved and fit perfectly, so now I can make them.
I have now crocheted quite a few hats for myself and others and it really has been like an evolution for me. I learned how from this great tutorial on Threadbanger and have experimented with my own variations since. I like to use a size 9.00mm crochet hook (the gold one!) and a chunky wool like Bernat Softee Chunky or Patons Shetland Chunky. I usually increase every other round according to how slouchy I want it to be and play with the size from there. Here are some patterns that I really like...
You can also check out Ravelry (you will have to create an account to view the site) for tons of great knit and crochet patterns and projects!