Why do guys stop talking to female friends while they're in a relationship?

Whenever a guy friend ends up being in a relationship, they stopped talking to me. It makes me sad and confuse why would a friend stop talking to me when they are in a relationship. Is it because I am a girl or if they actually have true feelings for me that I am unaware of? I see that my guy friends talk to other female friends but not me. Why would they stopped talking to me?
Why do guys stop talking to female friends while they're in a relationship?
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