Why is the trend to make separate phono stage

Why is the trend to make a separate phono stage. Say a high end pre-amp such as Audio Research Reference 2 you need to spend $ 10,000 for a line stage and another $ 7,000 for the reference phono stage. Almost every manufacturer has started to separate the two components. Is this to make more money selling two boxes or has technology gotten so sophisticated that it needs to be separate or lastly maybe only 25 % or less of the buyers want phono, so the manufacturer focuses on the 75 % population that need a line pre-amp. For us oldies it used to be easy to add a MC/MM board to the pre-amp to add the phone section. What happened??