Why is my guy friend sweeter and more friendly to others?

My guy friend and I talk about many private things, we have deep conversations and have known each other for a long time. But I noticed that he talks a lot sweeter to other people. When he sometimes sends me screenshots of conversations with others, I see that he talks differently to them. He uses more words, more emotjies and emotion in text. While with me he seems more cold and formal. He also never says anything nice or complimentary, even when I say something nice, he doesn't in return. I don't really understand his behaviour since we actually do talk about a lot of intimate stuff, but at the same time he comes across like he doesn't like me.

Why is my guy friend sweeter and more friendly to others?
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