As far as the city and its attractions - you're never going to be everything to everyone. Some players love being in the big city, but others would hate the brutal winters and would rather be in Florida. So, as nice as the Bruins' "Things to do in Boston" video is...eh. lol.
Now, as far as Boston becoming Free Agent poison...it could be getting there, if it's not there already. The perception of "defense is the first, second, third, and fourth thing we do" may be jarring. FAs may not care as much about "Clode doesn't play kids" if they're not kids themselves...in fact, they may see it as an opportunity for ice time.
The fact that we've managed to finish in the worst possible position two years in a row does not bode well. Trade deadline 2015: lose two seconds and a sixth round pick. Trade deadline 2016: lose a second, third, fourth, and fifth round pick. You have to wonder wat the goal of the team was in those moves - and you have to be a little cynical.
Also, there's taxes. I don't know the relative tax rate for all teams, but I know it varies. I know Florida can be attractive to many players for that reason, and I can imagine Massachusetts isn't as attractive. The number that they sign isn't the money they take home - a smaller contract elsewhere can net them more money.
That said, the fact that Boston has spent, and, for the foreseeable future, will spend to the cap is reassuring to players. At least you know your team will spend to cap, and you're only bargaining against "funny money", and not hoping that revenue will come in.
Media market is also a thing that some players may hate, and some may love. I don't think the "hometown boy" is an issue when you're a FA - by the time you're 24, I think your dream of playing for the Bruins has given way to the real world.