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

U@stereo5 
interesting, that you've owned 3 different VPI tt's, and you had the same problem with rumble, until you inserted a different TT.  Hummm?  Makes me think.

@tooblue 
i have a 3" maple platform, mounted on top of multiple 2" square rubber/cork/rubber isolators, on top of my wall mount.  However, I agree with you that, "with a table such as yours there should be no need".  Unfortunately, the need is present.

To restate my original question, why wouldn't the manufacturer of a high end phono preamp include an option to include a rumble filter.  If it's not needed, the user could disengage the filter, if it's needed (and obviously there are many others who could use this option) the user could choose to engage it.

Thank s for these quick responses to my question.
 
First:  @clearthink 
my analog system is a VPI Classic 3 TT, using either a Lyra Kleos Cartridge 0.5 mV, or a Spectral Reference Cartridge 0.2 mV. Using High Fidelity Reveal interconnects, into a Acoustech (Sutherland) phono preamp.  The TT is wall mounted, on the wall behind the speakers (Legacy Focus SE's), augmentedwith a pair of REL Storm III subs).

Second:  @lewm 
i am using a KAB rumble filter (with great success).  It is wired in to my Tape loop of my preamp (Audible Illusions L3).  I notice absolutely no degradation of sound when it is engaged, only the removal of an rumble.  My room is 14 1/2' x 19'.  At low volumes, I don't need the rumble filter, but at any 'realistic' volume (90db or above), I need it. The way my room is set-up, there is no way to move the TT to a different location in the room.

@wlutke 
its been maybe a year since I have lubricated the main bearing, but when I did, I didn't notice any change.  However, thank you for reminding me that it's time to do that again.
Also, isn't acoustic feedback the same as rumble.  If not, what's the difference?
@dwette 
a rumble filter may be a band aide, however, when engaged, I notice no loss of anything (transparency, detail, staging, etc) other than the pumping of my woofers.
@nrenter 
ok, so in the purist form, inserting a filter in the circuit may not be 100% kosher, however, if your traveling down that avenue, why do designers use crossovers in their speakers rather then design them cross-overless, why use a speaker cable with connectors on each end (rather then use bare wire, and solder it directly to the amp/speaker), why do designers of electronics use IEC connectors for the power cable, rather then hard wiring it (as some do) on and on.  These all affect 'ultimate' transparency, and are design choices.  I just don't believe that any of the things you mention can't be done with no loss of performance, or ultimate cost (1-another switch in this signal path....how many switches/connections  are already in the signal path, are you saying one more switch is going to degrade the sonics to the point where it's so audible that it is going to degrade the sound of your system to a point of dissatisfaction?      2-, after all, in a phono preamp costing several or more thousand dollars, how much more can a 'high-quality capicator' add to the final cost of a product? 3-a change in the circuit design...ok...I agree with that.  I am not trying to be combative with what you are saying, I just believe that these items that you mention can be dealt with in an effective manner.  Happy New Year!

There are just too many factors that create rumble or acoustic feedback (still don't understand the difference), and there are too many people that experience this problem.  I use my KAB rumble filter, with no loss of sonics, so I want a phono preamp with this included.  The only negative I have with the KAB is that another set of interconnects is needed.

@dwette 
Happy New Year!
when I engage my KAB (in my tape loop), I hear absolutely no degradation in sonics, so, as you say, I guess it is system dependent.  So, what was the root cause of your problem with rumble, and how did you correct it?
Thanks!

@lewm 
sorry, don't mean to sound as if I'm arguing.  It's a New Year, and I have too much to be thankful for!
My TT is very well isolated.  I can literally do jumping jacks directly in front of my TT, without affecting the tonearm while it is playing a record.  So, no problem with foot falls.  I believe the problem is acoustic feedback (volume low....... no rumble, turn the volume up....rumble).
You bring up a great point about the matching of my Cartridge and tonearm.  I will check on this!  That may be the problem.  Thanks for that suggestion!
Bottom line, like you,  I would like to identify the source of the rumble, and correct it, rather then use the KAB filter (however, I really hear no drawbacks when using it).
Hope your having a Happy New Year, and again thanks for your input!