Not sure how HDFC decides what card to offer and limit enhancement.
I got Millennia credit card LTF ~2 years back. Before that I just held one card (Axis MyZone), had used it just once 5 years back, that too it was for Amazon Prime membership offer (2 rs transaction which was reversed). And I was offered Axis ACE credit card which I had closed immediately after receiving (got angry because they charged me after saying FYF). That reduced my CIBIL to 780 from 790+.
Considering all this, not sure what logic HDFC uses to
But I started using credit cards for online purchases after understanding benefits. Recently I paid tax online of 1L+. But Millennia doesn't offer limit enhancement. Initially I received limit of 1.12L which has been increased to only 2.21L in these 2 years.