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

@louisl 

I believe the “rumble” you are experiencing is due to sound waves acting on the wall, where it is a moving diaphragm, transmitting the low frequency impulses back to the turntable, which has inadequate isolation. If you can move the speakers outside your listening room as a test, try listening to the same LP on the turntable on the same wall mount location. I believe you will find the “rumble” absent. 

Rumble is mechanical (audible and inaudible) noise transmitted to the LP due to inadequate decoupling between the LP and the platter and drive mechanism. Rumble can be mitigated by the combination of well-balanced motor (electrically and mechanically), well-designed and maintained platter spindle bearing, sufficiently damped platter structure and sufficiently resilient platter mat.