Why won't he text me, Only Snapchats me?

So, this guy i've been snapchatting a lot is super flirty on snapchat but has never bothered to text me. I texted him once and he responded on snapchat. We've always been friends but more recently he's been more flirty and we made out once. Just wondering why you think he is keeping everything on snapchat?
Why won't he text me, Only Snapchats me?
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