Very unlikely the OP is driving to the airport and going through security just to go to a lounge. Almost certainly, the lounge is secondary and there is a primary reason to be at the airport like accompanying a departing passenger, meeting an arriving one or having a meeting with someone.

Can you expand on the illegality? What law is being broken? Is it the buying a ticket without intent to fly or entering a lounge with a valid boarding pass and not proceeding to fly that would constitute illegality?

I have always wondered the airlines' logic in having a refundable ticket if buying one without intent to fly is a violation. What would be the point of having a refundable ticket if there is not a possibility or intention of possibly not flying? So the airlines make their money charging a premium for these tickets but when passengers decide to exercise the right to cancellation and refund then it becomes a 'violation'. Reality is it is all about money and not 'CoC'.

If there were no such thing as refundable tickets and OP bought a non-refundable coach ticket just for purpose of going through security (and if *G using lounge) and yet did not travel, would the airline cash the check and then still accuse the OP of violations? Unlikely as they cash the checks for hundreds of people daily who buy unrefundable tickets and don't travel (and sometimes never intended to) and never accuse those of violating CoC. This idea of buying a ticket without 'intention' to travel only becomes an issue when the ticket bought is a refundable one and never when it is unrefundable. Some years back someone posted his MP account was closed because he bought refundable tickets for his wife to accompany him on business trips and half the time she never did so he got refund. I bet if all those tickets were non-refundable his 'crime' suddenly wouldn't be a crime anymore and UA would have turned a blind eye and would still be enjoying his monthly cash donations.