Aside from occasionally looking cute, what biological / physiological benefit are they?
You got it. Looking cute. People with dimples may be more likely to mate and have offspring with dimples. Natural selection at work.
Actually, they are officially termed as birth defects. Funny, huh? Something considered an accident of nature viewed most often as attractive.
Everything is the result of a mutation. That’s part of how evolution works.
Not every by-product of evolution necessarily has a physiological purpose or benefit.