And even in the former, when there's hundreds of thousands or even millions of dollars/euros at stake, creating hype is simply beneficial for both parties and is expected, it's usually just an act for the media as well. There's practically no disrespect whatsoever between fighters who're not getting widespread media coverage.
I don't even need to bring up regular sports... When was the last time you've heard about a professional athlete who went "lol idk how i/we lost he/they is/are "dog"" or generally disrespect other athletes in press conferences or in any public/private forum for that matter?
And for the last paragraph I'm really curious of what you consider "regular" sports? If you're talking about for example fotball, basketball or hocket, I can hear it very often