Since the topic is underwear perhaps there are some good ideas out there for underwear that doesn't ride up. I have a round (fat) butt and finding underwear that doesn't ride up seems impossible.
The woman that suggested a tight leather jacket with no bra I'm guessing is a road rider and the needs are very different when you are riding roads rather than dirt. I don't know anyone that wears leather riding dirt. Even with road riding there is no way I'm going without a bra because it would be uncomfortable and at some point I will want to take that jacket off and there is no way anyone want to see that.
Each person's comfort level is different when it comes to traveling by motorcycles. Some are fine without the "luxuries" and others are miserable and consider them necessities.