They've wanted to do this for a while and some big publisher I think it was Warner Bros or Activision literally said "No, because we might have some legal claim to the IP, but we aren't going to check, if you do anything with it we will sue you."
Honestly, No One Lives Forever was a great game that would only be muddied if brought back.
Also, this article is wrong. You can still play both NOLF and NOLF2 on PC. There are fan patches that get them working on modern operating systems and fix up some bugs, while adding support for widescreen and HD resolutions.