It is very simple.. the benefits provided to the card holders are causing losses to the bank, so they cut down their loss by devaluing the card. Cutting down on the fee will give them more loss. They are doing a business.
ICICI report the shared limit for each card separately. So eventually the CIBIL would show higher limit against the actual limit. I have apay and sapphiro on shared limit and it is shown separately in cibil.
Customers with KYC verification have a daily transaction limit of 7,500 and a monthly limit of 30,000. Non-KYC users have a daily limit of 5,000 and a monthly limit of 15,000.