Originally posted by MysterD:2.Updating
...this is uncalled for, more so, on the SP portion of Half-Life 2.
The reason SP HL2 is updated so often becuase it is the core engine for Source. Thus an engine change is needed to CS:S or HL2DM, HL2 must also be changed as well.
Remember Valve is still using a smilar structure from HL1 where there's the Engine and then there are folders for each game and mod. When the engine needs to be updated, it registers in steam as updating HL2.