[Taniwha]

I'm not sure they're all that simpler, the basic plumbing probably hasn't changed much, it's just that modern fabrication tech means you can hide all the complexity inside

[damnitbuilds]

A single metal piece that contains plumbing inside it is simpler than a metal piece with attached pipes for that plumbing.

[jeltz]

In this particular case maybe but in general I would say it is the other way round.