Because when people make post on these relationship advice subreddits, we're only seeing one side of the story - their side.

There are 3 sides to every story (sorry gay people it's just for ease), his side, her side, and the truth. But we're only getting his or her side, 1 side when we read their posts. Not all sides.

I don't follow any of those subreddits, but I find it hard to believe there haven't been male posters with sympathetic stories or abusive female partners. So even I wouldn't be able to generalise like this.

In domestic abuse, it is more common for the male to be the perpetrator of the abuse, but female partners can also be abusive and it is under-reported. In some of these cases, it's likely that the male partner is afraid to speak up due to feeling embarrassed that he is receiving abuse from his girlfriend or wife. Something I disagree with entirely of course, but it is highly likely to be the case sometimes. Anybody can be a victim of abuse, even if you're manly AF lumberjack who is built like a brick shithouse.