I agree that it mostly causes unneeded confusion to have another arbitrary standard. I think usually they are created or perpetuated to give a minor convenience

I agree that it mostly causes unneeded confusion to have another arbitrary standard. I think usually they are created or perpetuated to give a minor convenience to a minority of specialists using it every day, but then they become popular and are constant obstacle for non-specialists. Other examples are the mole, angstrom, electron-volt, decibel and light year. It looks like the usefulness of BP to specialists is because the carbon dating is done in reference to a sample which was prepared at that time. I don't know why they don't convert to BC or BCE for an article that non-carbon-daters are going to read though.