Rozie wondered...

Sometimes people said things like "he was too grateful",
like it was some sort of insult or accusation.
It sounded as though the grateful person
 was going to spend all their time
 grovelling to, or sucking up to the person
who had done them some sort of kindness or favour.
A kind of  discreet division
where some people are one step down, and other people can
extend some sort of kindness and expect a lifetime of loyalty or debt.

Rozie didn't think that had much to do with gratefulness.
To her it sounded more like a class system.