Why are hickeys considered trashy or immature?

I am with a new girl now, and have never had a girl kiss my neck before, usually it's something I do for the girl. but anyway, we both get pretty rough and love it, and we both really love attacking each others necks too.

Unfortunately there are some visible signs of this roughness... but I feel like I should not have to avoid what I really enjoy in bed, but people have asked me if I am 16 or something. I guess I try and hide it, it is a bit tough for a guy though, I just try and wear collars or something. I was just wondering why they are considered so trashy/immature if we both just really get off on it?
Why are hickeys considered trashy or immature?
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