Bitbucket is in a weird position, in that Atlassian can't make the best Git hosting solution. It's not that they can't technically, it's just that they have complimentary products that cripples how good you can make code reviewing (crucible), issue tracking (jira), analytics (fisheye), wiki (confluence), and so on.
GitHub and GitLab are not bound by the same constraints, and can focus on creating the best end to end Git hosting product. While Atlassian has to be careful about cannibalizing other product lines.
We're a big Atlassian shop, and switched from Crucible to Bitbucket Server (then Stash). I do not get the sense that Crucible is the future as far as Atlassian is concerned - I believe they see Bitbucket Server as what they are going to focus on.
FWIW, with the latest releases, they've addressed most of the remaining features that were missing from Crucible, and I'm very happy now with the PR/code review flow in Bitbucket Server.
I agree; Bitbucket Server is a smash hit in big banks who are now moving away from SVN to GIT to stay relevant. It simply makes more sense to use BitBucket Server offering by Altassian given that most organizations already use Confluence for hosting their wiki.
GitHub and GitLab are not bound by the same constraints, and can focus on creating the best end to end Git hosting product. While Atlassian has to be careful about cannibalizing other product lines.