It's actually easier on the hands than using `_`. As on a standard (us, uk, chinese, etc.) keyboard underscore requires a shift-press whereas minus/hyphen requires a single press. It's a small change but you'd be surprised how much of a difference it makes, given that tokens are a significant amount of all writing when programming.
Not to mention, in my opinion it's more aesthetically pleasing, but that's just me :)
Sure, Lisps allow many more characters in the identifiers, including all traditional operators (makes sense, since the "operators" are just functions and they had to be defined somehow in the first place...) You get functions named like add-message! create-response/text bytes->string/utf-8 and so on. Kebab case refers to identifiers with words separated with minus sign, like some-class-member-doing-something etc. Some infix languages borrowed this, like Dylan and LiveScript, among others.
Common Lisp actually lets you use any string for an identifier if you wrap it in pipes, though you have to be a bit careful of casing in that case. Still for so many characters on the keyboard it's not needed to wrap which is so convenient as you illustrate.
Not as common, as it clashes with using '-' for subtraction, but as that's never been a problem for Lisp, it's quite common there. Perl6 went that way, too, despite having infix syntax. But hey, it's Perl, we're used to syntactical warts.
