It's a bad practice always since the user can easily choose if he/she wants to open it in new tab by themselv but not the other way. For a user there is zero benefits in this practice
For a user there is the benefit that they will not lose their presence on the website. Many users do not know how to navigate back.
Of course, in times long gone a new window would appear, and the pattern made even more sense than with tabs.
If you would have left out the word "always", I might have agreed that for this particular website and intended audience, it does not make much of a difference.
However, most people are not very skilled when it comes to computers.
Most people don't know tabs or multiple windows, either.