I have no first-hand knowledge of this situation. All I know is what I read in the philatelic press. Because several collectors have made similar comments, I have to believe there is some truth to the situation.
The USPS releases some press sheets to the public. Sometimes the press sheets have die cuts like the normal stamps. Sometimes the press sheets lack die cuts. My experience says that there is a small group of collectors who are interested in these items, but the following is not huge.
Several collectors have used the philatelic press to express their disappointment with the USPS. In some cases, the number of press sheets available for sale is not large (a few hundred press sheets). In one case, a collector says that they called the USPS to pre-order some press sheets and the representative informed him that all of the press sheets for that issue were sold to a single customer. Other issues have been sold out very quickly. It’s not clear if those other issues were also purchased by a single customer or not.
The USPS is just irritating the collectors who are interested in this niche of the hobby. Collectors like to complete a collection, especially when it involves newer material that should be readily available. The USPS is cutting back on the supply of some of these press sheets. In some cases, collectors are not able to purchase them at face value- they’ll have to pay retail price from a stamp dealer. This is going to cause some people to just stop collecting the press sheets.
Some collectors have had pre-orders accepted, only to have them rejected at a later date because the press sheets have sold out.
At first day ceremonies, the USPS representatives only have a few press sheets on hand (if any). This makes it very difficult for some collectors to get First Day cancels on their press sheet copies because the few sheets made available to the first day ceremony are gone very quickly.
Another complaint often heard is that the number of press sheets is unknown. In some cases it is right up to the first day of sale before quantities printed are known.
Some collectors have accused the USPS of conspiracy. I do not subscribe to that accusation. Is there mismanagement of the program? Yes. But conspiracy? I do not think so.
The USPS is killing the goose that laid a golden egg. Many of these press sheets are 100% pure profit for the USPS because they will never see postal use. Some collectors prefer the whole press sheet. Other collectors prefer imperforate pairs or some of the gutter pairs because they are smaller in size.
The USPS needs to get its act together and straighten out the press sheet program. They have been selling these press sheets now for several years. They should have enough sales history to know if they can sell 1000 sheets or 10,000 sheets to meet customer demand. They should be more transparent about how many sheets are printed for a given stamp issue. They need to institute a more fair policy for distribution so that one or a small handful of people cannot buy the entire set of press sheets. Everyone should have an equal chance to easily obtain copies from the USPS.