Since I was a kid, I failed so hard at being a guy. I've always been hopeless at athletics. My body type has always been pretty meek (let me not doxx myself and say more). I hate any sort of competitive environment. I can't hold my liquor for shit. I have a very high pitched voice and an expressive way of talking. Friends have described my voice as a "gay twang". My mum probably assumed that I was gay from day one, as I got a lot of "it's OK to be gay" from her growing up. Sadly I had too much soy or not enough soy, because I grew up attracted to women.
Maybe you old comrades remember, but schools in the 90s were full of homophobia. "That's so gay" criticised any action that deviated from some masculine ideal. I got this multiple times a day, and I learned to stifle my personality to avoid the rebuke of my male non-friends. I'm not even complaining, there's so so many that had it way worse than I did.
Nowadays it's great being a flamboyant straight dude. I can be as sweet, as empathetic, and as expressive as I want. I have cute and colourful clothing. I get really ecstatic around animals. I cry. People like me for being fun and engaged with stuff. Nowadays if some guy colleague says that's "gay" it's like 
"are you alright mate??"
I did go some LGBT events and actions in the past, but not a lot. If I do anything positive, it's to enforce no homophobic language with my students, which guys has gotten a lot easier in the past 20 years. Really, the kids nowadays are much better than we were. OK, I have hooked up with a few dudes here and there, but it feels like stolen valour to call myself bi.
So thanks a whole lot to all the queer people who have made my life much easier, when I've done so little.
I'd imagine most queer people don't want the spotlight. They just want to be able to exist, so normalizing labels like bi is a plus. Some agender/NBies give similar reasons as to why they don't identify as trans and no one whose opinion is worth caring (so excluding transmeds) about want people to be afraid of using the label for themselves. Likewise with people who would like to use they/them pronouns, but don't feel trans enough and are worried using their language for yourself. Bring a to use the pronouns you want, whether you are cis or trans, is something most trans people want.
Likewise, people who commit bi-erasure have opinions not worth caring about. Your type for guys doesn't need to be any sort of stereotypical guy for you to call yourself bi.
But there is no requirement to use such labels either.