Originally Posted by
Dark Soul # 7
Because they're part of a much more established organization than what Luke was trying to build, and they're arrogant as fuck, so they didn't fear a potentially dark side without any resources (as far as they knew) while Ben had contact with Snoke.
And these are the same Jedi masters that couldn't tell that obviously evil Palpatine was a super powerful sith lord or that Anakin married Padme. They were pretty damn blind to things and I don't think they ever knew about Anakin slaughtering the sand people or any of the other bad stuff going on within him.
And again, it was a moment of weakness that Luke immediately regretted, even before shit went to hell. I mean, if you prefer Luke to be a flawless and incorruptible paragon of good then that's fine. I just think it's more interesting, and perfectly in character, for him to be shown struggling with the dark side every now and again since that's a big part of his family.