Why can't us Gen 8 players have the BR 101, 182 and 403 layers?. I assume it's something to do with memory issues
It'll be because of memory limitations for PS4 and Xbox One, since the ICE 3 (and also ICE 3M) takes a big chunk of available memory as well as the 101 DLC and 182. The amount of AI services that may be present in the game also plays role to memory limits
From what Matt has said in the past only the variety of services adds very much to the memory usage rather than how many of any particular train there are, as in if you have 1 BR class 66 that's a lot of memory, but 100 of them doesn't take up much more. Add in a BR class 166 and that's another load of memory, but 12 of them not much more and so on
Ah in which case fair enough with that, and I can probably pick that including the 101, 182 and 403 to add more variety would cause last gen to struggle a lot