I noticed that Trader was inserted into 7DTD "for the sake of ticking the box". Because so many players complain about its imbalance. Especially early game when after passing the first tier you can get a bike without the need for personal growth. The trader itself in the concept that is available now seriously conflicts with the current mechanics of the game. For example, instead of collecting magazines to craft a gyroplane, it will most likely appear in the trader "Bob" by this point. Or you can speed up progression by buying magazines from him, or have the only way to craft dew collectors by buying it from trader. Or rob a trader's place because he won't do anything to you for it (yes you can rob them lol).
Let me give you an example of the trader element from a similar game with survival and zombie elements - Minecraft. There are villagers there that need to be protected. In 7DTD you can let a dozen zombies in and he won't care. All residents in a village may have different professions. At a time when traders in different specializations are scattered across the map. Minecraft has a kind of economy, and with new updates there is a need for gold where it can be traded with piglins. In Minecraft, villagers are a very important end-game resource. Because they were written as end-game mobs. Where a librarian can sell enchanted books. If, for example, you don’t want to rely on random enchantments. Moreover, in addition to librarians, there is Armorer, who sells diamond armor, even enchanted ones. Cleric sells ender perl and bottle of experience. Farmer sells golden carrots and watermelons. Fletcher sells arrows with unique effects. Leatherworker sells saddle. Toolsmith diamond tools with enchantments. Weaponsmith sells diamond weapons with enchantments.
In the case of Minecraft, the player needs to trade between villagers to obtain items; due to the fact that the player cannot craft many items, villagers can help in obtaining very specific resources. By the end of the game it becomes more of a maximum security prison. But still, in order to achieve the desired result, the player needs to improve the village from the very beginning. At this time in 7DTD you can only complete quests and buy existing items because you cannot influence the sell table on the trader. And it turns out that we have an end-game element that greatly harms not only the existing mechanics, but also the fun itself.
If you read my comments earlier I wrote that it's something like "Get into cold water and then into hot water". And I think this is a perfect description of what a trader is right now. And if you consider the fact that the quests from the trader are terribly boring and repetitive - then you get really bored. But to still get effective progress you have to go to him. At least for the filters. And if you consider the fact that players can safely add the crafting of water filters + the crafting of solar panels. Then the trader can be safely excluded from the category of necessities for the game. If the developers continue to forcibly add the need for a trader, it will be extremely bad
