Do you not feel that you are forced to carry your ICICI debit card wherever you go? Because I for one have 5-6 debit cards from multiple banks and a credit card also. But I only carry a Citibank debit card in my wallet.
If I attempt to make any net banking payment in for example my office via ICICI Bank and I don't have their card, I cannot make the payment (even though I know my internet banking credentials and have my mobile phone with me to receive a "one time password") unless I enter three grid numbers printed on the back of my debit card that I would not have with me.
So for me, all this grid based security just gets in the way. I've even asked them to disable grid based authentication for me and just give me an ordinary debit card (i.e. without grid numbers) as I don't want it but they say that they can't do that.