Yeah i noticed that as well. The game is made so that everytime they or you looks at something (It's shown in text of what they looking at) they start to gain lust by each time they look. This makes it so that you only gain lust from being looked at and not much from the sexual act, which is also why it can take way too long to build up lust unless you have a weapon that deals lust.
The main problem with it is that any character that is in high lust or maxed out on lust, will go and try rape a random downed enemy and make them possible to get revived and aggroed to fight again.
For the main character, they just take off their clothes and start masturbating.
This makes collecting your fav outfit to get dropped on the ground and likely picked up by your team that is naked, which can be fustrating in trying to find the ones that stole it from you.