Men watch porn because it is mostly positive for them.

Sure, they may get erectile dysfunction, but for many men that cannot get even one woman, that is not an issue. In any case, plenty of married men watch porn with no issues.

Porn is also a way to release sexual urges and forget about women or sex for a while, to concentrate and do something useful.

Porn is inferior to sex, and certainly not a replacement for it, but it can help men a lot.

Porn may also help with the gap between their woman and good looks. Their woman may be ugly, but porn is a good compensation, keeping the relationship stable.

Almost all criticism on porn is based on pseudoscience or moralistic arguments like "women being used somewhere for porn" as if women did not use makeup and other stuff made by asian slav*es.