“target=_blank” is not only bad practice, but could be harmful
mathiasbynens.github.io
mathiasbynens.github.io
Now a new version of Chrome comes out and the app doesn't work because the behaviour of window.opener has changed. What to do? Well, you can version lock to the newest version of Chrome that doesn't exhibit this behaviour (probably via an Active Directory Group Policy), or you can require users to use IE or Firefox instead of Chrome. Re-build the web app instead? That's pretty expensive and isn't on the roadmap until Q4 2017, but due to budgetary pressure may not happen until Q3 2018.
I'm not saying that this is a good thing; it's categorically holding us back. But it's how it is, and it's totally a people problem. Browser developers don't want to break existing code, and, because of that, organizations don't realize that their code is broken.
These large organizations, affected by purely hypothetical problems (nobody bothered to check for any real issues, or release a developer version of a fix), are a clear minority compared to the entities affected by the security problem that needs fixing. If that's how all the cruft gets added to HTML by a few people from 2-3 browser vendors, it's no wonder that it looks like it does and increasingly frustrates web developers to the point of resignation.