They're bothering because this is exactly the kind of support they promised for Left4Dead.
Let go of the silly nerdrage, you''re blinded by it.
Everyone expected more content from _Valve_. More campaigns, more survival maps and only thing L4D seems to get is Tools for community to make their own campaigns and survival maps so that Valve can concentrate for L4D2 instead.
However, the L4D2 Boycott group on Steamcommunity (that has around 18% of people compared to the official L4D Group) made Valve to change their mind. Now they promise more content for Left 4 Dead, the original one and promised not to ditch it when L4D2 is out.
I paid 50$ for the game, i assumed that it would get atleast 2 more campaigns before the end of the year + a lot more content than this, for free. Now 7 months passed after it's release and i've seen 1 _new_ map, survival mode lighthouse. Rest are just warmups for the maps that has been played over and over and over again. Then L4D2 was announced and it's not a suprise for me that a lot of people are dissapointed for the current count of DLC.
TF2 has gotten a lot more content since and so did CS Source too. In the first year of their release, there was amazing count of new maps for these games and new features. L4D is way behind in the schedule.
Old programmers never die, they just become managers.