Internal cable routing , it was unpopular and died a death about 15 years ago . Why are they bringing it back again , has something changed to make it a better idea now than it ever was ?

‘They’ hate mechanics….still.

aesthetics? clean lines.
better cable/ hose entry into mech/ caliper.
don’t have to compromise on design.
no cable rub on stays.

No sh1t and grit getting in the cables.

aesthetics? clean lines…..Meh.
better cable/ hose entry into mech/ caliper…..No.
don’t have to compromise on design…..eh?
no cable rub on stays….or just route them properly.

How easy is it to replace cables when they are interior routed?

A lot of them have a guide inside so you don’t have to try and fish the end of the cable through.

I know someboby who had to remove the bottom bracket in a Top Fuel to change the rear gear cable . Anyhow all of the percieved advantages that have been mentioned were present last time it was attempted .

don’t have to compromise on design…..eh?

you might want to design a seatstay with a lump here or a bump there which would impede an externally routed cable/ hose.
.
I agree with you by the way, I don’t think it’s worth it and can cause a lot of hassle, especially with brake hoses.

Do they tend to use continuous outers inside the frame with internal routing?

they should SBZ – but its when you get numpty mechs that dont know how to deal with that that the problems arrise.

Most of the haters pulled all the cables out and then went to fit their new cables – with great difficulty

There is a technique to deal with cables internally routed … makes it a piece of piss to change cables really

mostly these days ive seen them having liners internal which you thread just an inner through and the stop is at the frame entry point