Why do people go speechless while talking..Have no words ..Still Stay WARM!!?

[Blv'n'Get]

Ok one of my friend (guy) is less talkative..

Every time he likes my communication (mails ,chat ,face to face whatever)

I do lots of fun and chitchat kinda (yet warm personal touch) lights talks

However he always answers this way:

"As usual I have no words to say"….and smiles.

While I am very much expressive and communicative and he is not , I mean He could but don't know why he does not...(I am Aries girl btw)

What he must be thinking or bored of me??

Thank you ALL