Honestly what guy doesn't like boobs. That's the only reason I can think of. If you don't feel comfortable about it, then speak your mind. Hopes this helps.
Why Do Boyfriends Like To Kiss The Chest Area?
As a guy I can tell you that when a guy kisses you there it's an attempt to keep the moment and escalate the excitement.
A guy will kiss any part of your body that he thinks will turn you on; and I mean any part or area!!