Why does the Keijo anime/manga title have eight "!" characters? I found it interesting that in the Keijo title are eight "!", written like "Keijo!!!!!!!!".

Did the author ever tell what's the reason behind its title besides "for making the title eye-catching"?
Exclamation points in anime/manga titles is somewhat of an ongoing trend, and because of the ludicrous themes in keijo!!!!!!!! they jumped on the trend in a similarly extreme way as a sort of publicity stunt/way to attract attention. Some more toned back shows may use it to denote seasons (like K-ON!!) but for shows like keijo!!!!!!!! they are instead used to show a self aware, extreme and ridiculous nature.