Why so few speakers with Passive Radiators?


Folks,

What are your thoughts on Passive Radiators in speaker design?

I've had many different speakers (and like many here, have heard countless varieties outside my home), from ported, to sealed, to passive radiator, to transmission line.

In my experience by far the best bass has come from the Thiels I've owned - CS6, 3.7, 2.7 which use passive radiators.  The bass in these designs are punchy yet as tonally controlled, or more, than any other speaker design I've heard.  So I figure the choice of a passive radiator must be involved somehow, and it makes me wonder why more speaker designers don't use this method.  It seems to give some of both worlds: extended bass, no port noise, tonally correct.

And yet, it seems a relatively rare design choice for speaker manufacturers.

Thoughts?
prof
You wouldn't use them unless you need to use them, typically in smaller speakers to increase bass response. If you are designing largish floorstanders with large multiple woofers...why'd you need to use em?
Plenty of modern stuff:

Legacy Audio Signature SE and higher level Legacy speakers
Endeavor Audio E-3 MK2
Magico various speakers
Focal Sopra 2, 3

These are all ported or sealed twin woofer designs that go very deep, there is no need for passive radiators.