Pregnancy (3 kids, and I didnt stop boning just because she had a belly), breastmilk (I was grossed out by this, but dared to taste it... and suddenly it wasnt a problem anymore), and "public" sex. Although this one prob borderlines legal, but its past the 7 years so I'm prob fine. First was on our driveway in a cul-de-sac in a fairly busy neighborhood/street. We often had parties and bbq's in the middle of the road with all ~6 houses in the circle being friendly. Up against the hood of the car I started teasing her and she was afraid/embarrassed, but it was easy to push her past that and get her horny. Ended up fucking her right there on the hood of the car. If any neighbors had come out or even looked out the window (prob about 9-10pm, so dark but not too late) she would have been seen. That is when we found out that even though she was really embarrassed, she REALLY liked it. She came so hard and multiple times. Then a few years later, we were in an apt. The balcony was up against one of I would say the top 20 busiest roads in the busy state. Even at like 2am, there would be 20+ cars per minute driving by this 7 lane road. Same setup, she resisted, I got her in the mood, she stopped resisting and I fucked her right there on the balcony. Plenty of cars driving by. Again, she came hard as hell.
To clarify, I am not into the "let people see my (now-ex)wife naked" part of this, but the risk of being caught part, and the excitement and embarrassment she felt.
It's illegal where I'm at, but I just looked up the US states that allow sex/marriage and it seems to be about half and half. Pretty surprising variety too, I had no idea it was legal in states like cali and Vermont.
If I remember correctly, I think these laws were changed to allow for places where accidental incest was more likely due to lack of outside-blood. I read about it about this when I was looking into incest after finding I had an odd interest in it in porn games. I think I read that it was kinda globally banned in the US, but some places had to fight that because they found suddenly... .30% of the population was likely to become criminals. But I think that was a long time ago and no longer a valid reason and just hasn't been changed because nobody noticed enough to make a big enough issue out of it.