How do Dug Up Antiquities Lose their Provenance?

In the same post as the statement that “"Some ancient coins undoubtedly have not been dug up at all”, Californian coin dealer and no-questions-asked-antiquities-dealing apologist Dave Welsh writes:

When I prepare a certificate of authenticity, I state provenance and if it seems appropriate to do so, may also state it in a listing [...]

In fact if one looks at the Classical coins website, the number of coins listed in his shop are given any kind of provenance that can demonstrate they were excavated and left the source country legally is minimal.
In the "Greek" section, only 13% have any sort of mention where they came from, but in most cases this refers to them coming from the collections of persons apparently still alive with no information on how and when they entered those collections. This of course tells us nothing about their origins, and how and when they left te shores of the Mediterranean to end up in a US dealers' tray. Likewise in the new listings section, the Roman provincials and the "Persian" coins (he has an awful lot of these, including the Orodes II coins I discussed earlier here)

It seems that about 90% of the ancient coins currently on offer by Mr Welsh have no provenance. Some of course will have come from some old collection made in the nineteenth century and taken across the States in a waggon train bound for California. Others however will have been dug up more recently and found their way to the US in various ways and at various times. To judge by Welsh's site, collectors are not at all interested in the stories of these coins. Information on this is routinely (Welsh says "traditionally") erased as the commodities passs from hand to hand. In other cases, the information is deliberately suppressed by the dealers for various reasons.

Mr Welsh is guilty of this too. A while back I drew attention (first on Unidroit-L, possibly on Moneta-L and more recently on this blog) to some special lots he was selling of "Roman provincial" coins.

I see that "Classical Coins" currently has job lots of uncleaned coins "from Thrace and Lower Moesia" (ie the regions which roughly speaking are now the modern state of Bulgaria with its antiquity laws).... http://www.classicalcoins.com/product845.html;
http://www.classicalcoins.com/product846.html

The first link is broken, the second still works at the moment. I have subsequently mentioned these coins ("coins that we were able to acquire in quantity and can offer to the collector at particularly attractive prices") a couple of times here and here.
So I was interested to see today that the description of where the coins in these special lots come from has been edited out. Why? Is the dealer trying to hide an uncomfortable truth when the looting of coins and artefacts from precisely Bulgaria was the subject of wider discussion? Why does he feel he can he not now tell his customers from which region of the Roman Empire these coins came from ,when earlier he was doing this on his website?