As I understand, that's Steam's doing, not the publishers.
I saw several reports of it.
Its not the developers that set pricing? My understanding was that Steam asks publishers to set sale prices (for those that want to participate) and it was up to the developers to do so.
Obviously Steam's interest is for a higher sale price, because their cut is based on a percentage of the total cost...but I don't see how they would tell Rockstar not to lower the price unless they have information that Rockstar's own Sales/Marketing team lacks regarding consumer buyer behavior (and that may very well be since steam has sales data for all games and can assess whatever it wants).