if you don't think that any product has the right to be sold by the people who create it, and instead have to submit to a large corporate entity to sypher away all their profits, then you're deranged. and I can't capitalize this enough: THIS IS THE VERY FUCKING REASON THAT STEAM WAS INVENTED IN THE FIRST PLACE, SO THAT VALVE DIDN'T HAVE TO HAND THEIR PROFITS OFF TO VIVENDI, A 3RD PARTY PUBLISHER. Irony abounds. although if "analogy" flew over your head, i don't have much hope for you coming to terms with the irony of your argument.
I'm not sure why you keep talking about rights. This isn't a legal matter. Of course Rockstar has the right to not use Steamworks. However, is that in the best interests of its customers? The answer is "no." Customers want Steamworks. That's why the vast majority of customers are going to buy GTA5 on Steam. Rockstar is selling GTA5 on Steam because they know that Valve's 30% cut will be more than offset by the sheer bulk of sales that Steam provides. GTA5 will generate more profit from Steam than it will from any other distributor, including Rockstar's direct sales from their own website.
Also, your comparisons to publishers are misinformed. Most developers rely on publishers to fund development, not just to handle distribution. Valve does not fund development of third-party games. Valve created Steam not to avoid publishers (because developers still rely on publishers and publishers are still selling games on Steam) but to cut out retail. PC gaming was shrinking in retail and publishers needed an alternate, more reliable source of revenue in order to justify PC development. Steam provided that by removing manufacturing and minimizing distribution costs. As such, the profit margins for digital distribution are higher than the profit margins for physical distribution. Were it not for Steam, most publishers would have abandoned PC development by now.
Ultimately, it boils down to giving customers what they want. Customers want Steam. By making Steamworks the standard DRM for GTA5, more customers will be happy and therefore more likely to buy the game (or pay more for it). This isn't about rights or principles. It's about business and using Steamworks is best for business (which is why every publisher except EA, Ubisoft and Rockstar now use Steamworks in all of their games).