Lots of top athletes have superstitions about abstaining from intercourse prior to events - some are very extreme, with fighters isolating themselves from their spouses and training for months without any release before their MMA fight/boxing match. Some say they do it for, say, just a week ahead of time, etc.
There are a few who have the opposite philosophy and claim to actually do it more in the week leading up to the fight.
It's really a massive point of contention because some people claim it is a mere superstition while others absolutely will not break their routine.
There is also the famous incident where Bobby Fisher says that he performed poorly at a tournament because he had sex after the first night and the experience totally removed him from his focus...
This might be why it impacts fighters and certain people whose lifting styles are really about maximized performance and not a routine... If concentration is interrupted, it can result in very poor output. Like I can see how someone who is very intense about what they are doing and requires total focus would be interrupted by any form of sexual distraction. This is probably very, very relevant to guys who are fighters...
This might also have to do with perspectives on sexuality - people who ascribe a lot of meaning to it versus those who do not...