power supply miniaturization?

Many preamps and digital players had outboard power supplies.
What new technology has made the big box power supplies redundant?
The newer external power supplies are used for a couple of reasons...
1. low cost - one supply can be used for many different devices from many different manufacturers
2. having them outside the box lowers the noise floor by eliminating mains interference
3. switching supplies tend to be smaller and more cost effective to produce.

I replaced mine with a much better power supply and it resulted in huge improvements in sound quality