Because the widespread perception that Buffalo isn’t a desirable place to play hinders the team’s ability to attract quality free agents, get players to waive NTCs for trades, and so on. Berglund passing up millions to get out of Buffalo (for whatever his reasons) certainly doesn’t help with that stigma.
Buffalo isn't a desirable place to play currently because we've spent several years being intentionally bad and are struggling to get out of that loop. Winning makes people happy to show up, end of story. If a player is specifically looking for bright lights, big city, always great weather, Buffalo will never rate anyways.
I highly doubt Berglund's issues makes anything resembling a dent in attracting FA's. Skinner waived his NTC for Buffalo, or have we already forgotten? It's almost like each individual player has their own likes and dislikes and we have no idea how much the "city" really makes a difference.
Winnipeg was long considered the worst place in the league to get traded, you know what changed that? Not being a terrible hockey team.
Free Agents are a really small part of the team make up and often involve either straight money or fit and development (Buffalo signs some every year) and NTC's being waived are on such a case by case basis that winning probably solves 90% of that issue.
It's also all irrelevant to your suggesting that he basically walked away from millions of dollars just to get out of Buffalo which is inane.