The company has been at that site since 1886. It's centrally located between NYC and Philly and has access to the Raritan River and the Delaware-Raritan Canal. Since they actually own the property and don't rent office space like a lot of large companies, moving represents a significant cost.

That aside, the company did consider moving back in the 70's when the area was far worse than it is today. Leadership decided that the company has a responsibility to the community it's located in, so they partnered with the city to invest and make significant infrastructure improvements.