How come only 1 or 2 cartridge makers offer a tune-up after run in?

Nakatsuka-San at ZYX never tune or repair his cartridges, i think it’s sealed design. Even if you’re buyin cartridge from official dealer it can’t be repaired or retipped by Zyx, you will get absolutely new cartridge with different serial number for special price when you’re dealing with official distributors. That’s what happened with my Zyx Premium 4D when the cantilever was broken (i will remember that day forever). The policy of ZYX in this situation is to supply brand new cartridge for their customers with discount! I think for premium clients it is much better solution to get new cartridge instead of fixed old one (or retipped) etc. This is High End and the price is high. It was the main reason for me to start searching for top vintage MM cartridges, i do not regret that i don’t have my Zyx anymore.

P.S. No tuning from ZYX, only diamond cleaning as far as i know.

I wonder what they do in their "tuneup"...   I have had numerous cartridges and none offered this service. I personally readjust my arm as the cartridge ages....VTA, et al.  One of the pia pleasures of vinyl.

Just read the latest Crimson review in Enjoy the music and the reviewer covers this subject.

Never owned one. Never read anywhere that this was recommended. Is this something a buyer finds out after purchase?

@testpilot My understanding as heard from VDH dealers is that it isn't about QC, it's about how the stylus wear in the first 300 hours upon inspection let's VDH see how to adjust the suspension to make sure that on the table that's being used the cartridge will perform as close as possible to its design. Maybe VDH stylus vs. other shapes is part of the reason why they do it and others don't? Your last suggestion could just as easily be the reason...maybe someone else can tell us both. Cheers,
Spencer

Perahps, there is better QC with modern cartridges which negates the need for a follow up tune-up, or there is not enough cartridge artisans within the manufacture to perform a follow up tune-up.   

Sure it's great that Brooks Berdan adjusted the setup after a cart's suspension is broken-in, but isn't that different than what VDH does and actually opening up the cart and adjusting the suspension, rechecking channel balance etc. inside the cartridge itself? 
I also have owned a number of VDHs, agree with OPs observation that the adjustment or "tuneup" does improve the sound and was curious about other cartridge manufacturer's viewpoint(i.e. why it's not their practice) on that idea.Cheers,
Spencer

Analog expert Brooks Berdan always broke-in the cartridges he sold and installed on his customers’ arms, not letting them leave his shop "in the box". After running the cartridge for a certain number of hours, the cartridges suspension having been fully exercised and stabilized, he would then do the set-up all over again. That’s the right way to do things, but is uncommon.