I'm sure this has been covered many times before so forgive me but I haven't been able to turn up an answer by searching.

My question is how upset Delta gets if you intentionally don't make a connecting flight.

For example, let's say I book a round trip flight from LAS to BOS connecting in CVG both ways. On the way back, I really want to end my trip in CVG and not continue on to LAS but I book the full round trip because it is cheaper.

What happens? Do the Delta revenue police come auditing your account or what? Anything technically illegal about this?

I assume you don't get credit for the segments not flown since they never run your boarding pass through the scanner.