Why don't all phono preamps include a rumble filter?

My personal experience is that a rumble filter is a band-aide (and a poor one at that) for not correcting isolation/vibration issues. I learned that the hard way and now have a KAB RF-1 Rumble Filter sitting unused (and unneeded) in my closet.

@stereo5 In the end, my primary problem – after I got isolation under control otherwise – was the tonearm. I was using a Clearaudio Magnify. The magnetic bearing caused severe woofer pumping on certain recordings. After doing everything else I could to isolate the problem I finally changed to a tonearm with mechanical (precision ball) bearings. That was the night and day difference that finally solved my rumble issues. I also had to correct some isolation issues, and now I can play bass heavy records at high volume (and that’s with Confidence C2s and a pair of RELs) with no rumble issues at all (unless the record itself is mastered badly in that regard...rare for my collection).

@louisl 
I guess it depends on the system, but when I engaged my KAB RF-1 – whether in a tape loop or inline between phono and pre – I experienced a loss of SQ. That is why I made the effort to fix the root cause of the problem, rather than patch it with a kludge.

@louisl
Other than getting my turntable properly isolated: I use a Solidsteel WS-5 wall bracket with 3" end-grain maple block. The turntable (Clearaudio Ovation) sits on that. I have changed the OEM feet to a set of Harmonic Resolution Systems (HRS) Nimbus pucks (I have also tried isoAcoustics Gaia and Orea feet...they all work).

As explained in my post above, the real source of rumble was the Clearaudio Magnify tonearm I had...the magnetic bearings were the issue. I changed to a Clearaudio Universal arm with mechanical bearings. Problem solved completely. My KAB sits in a drawer. It isn’t necessary. Fixing the root cause is still the best way to solve problems.

Likewise, Happy New Year to you and everyone else.