Because, slowly, very, very slowly manufacturers are realising that it is all the little things that count: the quality of the connectors, volume controls, power supplies, interference countering measures. They don't talk about it because it isn't sexy, and because the cummulative effect of sorting out all these seemingly minor elements is often hard to measure.
The equipment today sounds better because the quality of the elements making up the system are balanced, there are less poor performing items in the mix. And all those people who don't believe this, who own modified R2R had better pull out all their tarted up bits, and replace with stock standard parts as per when the machines were manufactured.
Frank