It's a matter of the games not living up to the previous versions. FEAR 1 was awesome, that's really all there is to say about it. I liked it enough that I bought it twice in retail (lost the first disk) plus the Steam version (had the expansions bundled). I still play it occasionally. FEAR 2 was alright, but it wasn't able to match the creepy factor like the first. It was obvious early in the game that Alma wasn't a threat, and the console friendly gameplay felt like running around in god mode. That's aside from the odd "minigames" like the mech suit, which actually WERE god mode unless you went AFK to grab a bite while being shot by multiple enemies. I preordered FEAR 2 based solely on my love of the first one. After playing it, I didn't bother with the DLC. I didn't hate the game; it was alright. It just felt more like a generic FPS with "super soldier vs monsters" than a FEAR game. HL2, Halo, etc did it better.
From what I've seen, this newest version of FEAR is moving even further away from its roots than part 2 did. Growth is needed in a franchise, but there's also a risk of moving too far away from what made it famous in the first place, which is what they have done with FEAR. I'll buy the third, but I won't preorder it, and I'll probably wait for a substantial sale.