Even when you request to enter the lounge and show your credit/debit card for complimentary access, they would seek your boarding pass.
2 months back, while I was travelling in an early morning flight, I was declined an immediate lounge access as I still had more than 2 hours to my flight. Bangalore Airport, the one that is outside city limits. So ticket/boarding pass is very much necessary.
The economics behind all these 'chintu' cards offering lounge access (which is quite costly otherwise) is that they know most of their customers would never fly, or even if some of them do it would be once or twice in a year max, so overall costs as a whole would be nothing extraordinary. No disrespect meant to anyone but this is how it works.