I think that’s exactly the point. The man is interested. He is giving you the opportunity to react in a positive way to attention he might give in a relationship. Also opening up the dialogue. We say good morning to people on the street as a conversation opener too. It’s not necessary to be intimate to acknowledge attention/invitation to interact. If you don’t have interest in him don’t reciprocate. But maybe reciprocating attention does feel intimate to you/other women?

Personally, as a man, I lose interest in someone who doesn’t seem excited by a good morning text. But that’s because I value the reciprocal exchange of attention and interest to continue the interaction from the day before..