Simplicity is easy to claim and hard to demonstrate. The demonstration is a parts count, and what happens to a system when each of those parts fails.
The parts that are not there
A pump-free system has no pump, and therefore no power supply, no transformer and no pressure switch. It has no plug, so it needs no socket under the sink and adds nothing to a distribution board. It makes no noise, because the thing that made the noise is absent. None of those parts can fail, because none of them is there.
It is worth saying precisely what that does not mean. Pump-free is not pressure-free. These systems work because the mains already supplies pressure, and each one carries a minimum inlet pressure below which it will not perform to specification. And it is the under-sink and commercial range that is pump-free: the A95R has a 25W priming pump, because it is built for river and lake water, where there is no mains pressure to borrow.
Fewer housings, fewer joints
A conventional multi-stage system puts each stage in its own housing, and every housing is a seal, a bracket and two connections. Integrating stages into one cartridge body reduces all three counts at once. Fewer joints is fewer places for a slow leak to start inside a cabinet nobody opens for six months.
What simplicity costs
It is not free, and it would be dishonest to present it as such. An integrated cartridge is replaced as a unit, so a stage that is still good goes with one that is finished. A design without a pump has to be sized around the pressure it will actually be given, which makes the survey before installation matter more, not less. Those are the trade-offs; they are the reason the finder on this site asks about pressure and source before it recommends anything.
