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

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.

Nakamichi also used to make an inline filter that I believe was down around 10 that worked very well, with that said with a table such as yours there should be no need and only take away from it all.

I had 3 different  VPI turntables, a HW19 MK4, Scout And Prime.  All 3 of them neccistated a KAB Rumble filter.  Like yourself, I couldn’t move the turntable from its position. I tried everything I could think of, 4 different types of platforms, different kind of footers, etc. Nothing changed the rumble.  Recently I switched to  Technics SL1200G turntable, using the same cartridge and lo and behold, no more rumble.  It must be something in the design of the VPI tables that helps amplify the rumble.  At any rate, I am very pleased now.  

I was Just thinking, as you and I are kind of in the same situation, one of being shoe horned into a given set up in a less than favorable room, you might want to try a Symposium ISO platform between your table and shelf in your wall rack. 

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.