It happens for one reason or another. Blocks get closed. Stands are made family-only. Upgrades to eg press facilities. Over the years BL has seen numerous changes, and not everyone has welcomed them.
For most of its existance the kop has been a fully standing terrace until it was converted to an all-seater following the Taylor report. Despite this, fans have always stood up at the top, and the club has been threatened with the full or partial closure of the kop due to this.
Now safe standing has become accepted, the club was faced with a choice. Allow standing in the areas where many already stand, or continue to prohibit it and face sanctions. It chose to convert 3000 seats to safe standing, a decision that most are happy with.
I get that some are unhappy, as they were when H Block was closed, when the John St was designated the 'family stand' and when some South Stand seats were removed to accomodate new press facilities. There's no way to please everyone when developing the stadium.
If a bunch of people who know each other don't want to stand they can all request a move. If some prefer to stand than be with mates who move, so be it. By and large everyone on the Kop is friendly and will talk with their neighbours.