Basically an accessory ..for most. My dog has a blue one with little canadian flags all over it that I usually put on him while camping. I think it started because it stifles the noise of his tags a bit (I don’t like the dingling noise). Lol also because, well, it makes him look cool :P
I know some people use them as a replacement for collars as well (I notice it more on rural/farm dogs).
As @crisw said, some use it to cover questionable collars.
As @ChocolateReigns already explained most of the time groomers are the ones to put it on dogs. I think they do it for two reasons. One your dog looks cute with it on and two it will draw other dog owners attentions to your dog and how cute he looks. Prompting the usual question: Where did you get your dog groomed? It helps to advertise. Plus puppy looks like he or she has been pampered and your more likely to bring your dog back if you feel he had a good experience.
shhhh….my dog told it to me in confidence
It’s a super secret signal to other dogs. Certain colors, tied on right or left, pattern, the way it’s folded, freshly pressed, or scruntched all have a meaning only our dogs know.
I would say it’s just an accessory. Usually I feel the need to roll my eyes at people that dress their animals up, even a fancy collar can irritate me. However, I know a Skye Terrier who is a lovely dog once she trusts you but is not great with strangers. Anyway, her owner decided that by putting a bandana on her, it would make her look a little less intimidating when she barks at people (!) The funny thing is, it kind of worked! She will stand by the window and bark at people when they walk past and before the bandana people would either step further away from the window (because if they didn’t the dog would just smash the glass and hurl herself through~) or look at the noisy mutt and frown. Now, with the bandana their reactions are different. They may jump at first when they see her yelling at them through the glass but as soon as they see the bandana they smile!
Ember, my golden retriever just looks plain cute with a pink bandanna on. Im pretty sure more chicks at the dog park talk to me when she has her bandanna on.
Molly is getting spiffed up today with her red bandana to go for a much needed walk in the park. You never know what you might find or run into so you should look your best.