A large part might have to do with internet pornography. Masturbation is already known to lower T levels temporarily. Do we know what the long term effects of chronic masturbation are?

Before you prepare to downvote me for having Christian sentiment, know that semen retention is actually an old eastern practice known to boost libido and health.

And yes, (ready for the pedants), prostate health has been correlated to unclogging old fluid in "the pipes" but that doesn't require the frequency of masturbation that is commonly practiced by single men in America.

The mental effects of constant video arousal have already been documented to be the cause of underperformance and erectile dysfunction in men. It's not a far stretch to ask if this psychological effect has a feedback mechanism coupled to libido and testosterone production.