RIAA, Decca, Columbia
As I understand it that is because the Labels themselves changed the recording process over time.In the case of the RIAA curve, to change that the label would have to dig into the pre-emphasis networks in their LP mastering electronics. That's non-trivial since they are trimmed to match the cutter head in use.
However a label isn't doing well to deviate from the RIAA curve since most of their customer base won't have access to equipment that has their curve- in a nutshell, its a non-starter.
The older EQ curves- Decca, Columbia and so on won't be changing, since they've not been in use since the early or mid 1950s.