It wouldn’t be a reverse incentive, it’d be an added incentive on top of the existing one. If sirens are only audible near traders, then it adds incentive to stay near traders. There's already incentive to be near traders, since that’s where you get missions, turn in missions, and do your trading. Plus some less tangible benefits, like potentially taking advantage of a plot of indestructible blocks on one side of your base.
If you’re asking why incentives to stay near traders are bad in the first place... I think it’s bad because as a developer you want to utilize all the content you made for people: the whole random worlds you’ve put so much effort into creating. The game is more boring when every playthrough, you’re making your base on the same plot of land next door to one of the same 5 trader compounds. Like, I can more or less recognize the empty lots that RWG puts on the other sides of traders by their terrain and deco features by now.
Wouldn’t it be fun to build a base on a mountain, or on an island, or on top of a big ore mine? Sure, but it’s never worth the effort because it’s so much more efficient to be neighbors with a trader. Building anywhere else is pretty much a vanity project. Adding a kilometer or more of round trip travel time because your base is out in the boonies just has no appeal.
Edit: I suppose I should add that I’m coming at this from the perspective that the siren provides useful information and therefore is good. If your feeling that it’s “cringe sounding” dominates over any feeling of redeeming quality, then I see how putting it near traders would be a reverse incentive.