Its not a "growing unclean perception". Euphemisms like X is joining Y, or X is joining the Y family, etc., have been common in corporate mergers and acquisitions for a long time.
The audience for the euphemism is mostly customers and employees, the impression that is sought to be created is that existing customers interests will continue to be served -- but even better by the new, bigger, stronger team -- and that employees are becoming part of something that includes their existing firm (and that they aren't going to be sacrificed.)
Of course, euphemisms alone can only do a limited amount to mitigate customer and employee concerns, but their cheap, and everyone has used pretty much the same ones for decades.
The audience for the euphemism is mostly customers and employees, the impression that is sought to be created is that existing customers interests will continue to be served -- but even better by the new, bigger, stronger team -- and that employees are becoming part of something that includes their existing firm (and that they aren't going to be sacrificed.)
Of course, euphemisms alone can only do a limited amount to mitigate customer and employee concerns, but their cheap, and everyone has used pretty much the same ones for decades.