I completely disagree.
Do you know why currency, such as the pound and dollar, is used? It's because it is a common thing that people want. Without it, you have to trade items for other items, which isn't as easy to do as you might want something from someone else but they don't want what you have.
That is the same for real life as it is in minecraft - There is no currency in vanilla minecraft, so vanilla shops deal with trading items.
Sure, you can make people pay with an item that can be sold on the market, but then you're placing a limit on your customers somewhat, as they have to use that item to pay. It also over-complicates the process as it makes it harder to estimate the actual price of goods in $s, for both seller and buyer, which also makes it harder to compare prices between merchants. Personally, the currency I use is stone and gravel, depending on how expensive I deem an item.
Also, there is the building process of a vanilla shop - As far as I am aware, all designs require nether quartz, which is easy enough to acquire on a fresh nether, but not so easy to acquire on the nether we have, as you have to go very far out to even get any, which takes quite a while. The designs of vanilla shops take up far more space than a chest shop from a plugin, and these plugin chest shops are much easier to build.
I'm of the opinion that the reasons against chest shops are flimsy; The main argument posed against them is that they could be spammed everywhere, but surely chests can be spammed everywhere as they are anyway?
Although, I'm under the impression that this opposition is raised purely for aesthetic reasons; IE, the people in charge don't want to see loads of chest shops everywhere as it wouldn't look so good. I am unsure of how the chest shop plugins work though, so is it for performance reasons or do the chest shops take up as much storage space as the sign and chests would by themselves?
It's worth noting that these vanilla chest shops can also be place anywhere. The design I use is fairly compact and would be easy enough to build out in the open so people could shop there
I know my opinions alone won't change the minds of the people in charge here, but I've seen it pointed out that this suggestion has been brought up quite a lot, which shows there is demand for such a system to be in place.
Overall, I can see adding chest shops as only being a good thing;
It will make trading more secure as the process of receiving an item and paying for it are done at the same time.
It will encourage more people to open shops and therefore make the server more social.
Sure, you'll get someone that will try and use the system to grief, but that will be the case with most features, and you can't make everything 100% grief proof unfortunately. All you can do is punish those that do grief.