Exactly this!
Firstly, deals info being readily available would hopefully increase competition amongst the retailers.
Secondly, I'd think the retailers themselves should be interested in their deals being accessible by the widest audience possible. Because why they make deals in the first place is to attract new customers, and if the only way to learn about the deals is subscribing to their newsletter (which means you are already a customer) or finding their website accidentally, then this means that the strategy is not really working as it should.
I was going to suggest creating a (moderated) deals thread, however the issue with that might be that the forum is owned by a specific retailer who might be opposed to promoting other retailers via their platform.