First laundry detergent/soap with FWA?
Rinso by Lever Bros. introduced in 1947 or 1948, cannot recall when. Later on came Blue White, La France and then many other detergents such as Tide, All, Bold and virtually everyone else added fabric whitening/bluing agents.
Some of the older products such as vintage All "with Bleach Borax and Brighteners) must have used both bluing agents in addition to OBAs. I say this because when a sour is added to the final rinse after using such products one finds the same tell tale "rotten egg" whiff that comes from doing the same when using some types of true bluing. This scent is caused by a chemical reaction of the acid pH to iron found in certain bluing agents.
Also some vintage products like All (with the Three B's) leaves laundry noticeably tinted a bluish green. Same shade as some bluing agents. In fact one reason stopped using the vintage All in my stash routinely is that found whites/colours taking on a dull bluish/green tinge that comes from excess use of bluing.
In fact when laundry comes out of washer after using All when held in bright light one can see the bluish/green effect quite clearly.
Why fabric whitening agents? Because natural fibers such as cotton, linen and even wool aren't white to begin with, but bleached to reach various shades of that "color". However bleaching alone does not remove the often yellow tinge that results so fabric whitening agents are applied at factory to textiles to give them that "whiter than white" effect. In the old days it would have been a type of bluing but not always.
If anyone uses or collects vintage linens or comes across something made say before 1930's compare it to modern offerings. You'll notice a difference between a "white" shirt or sheet from back then to something from say the 1950's onwards. That difference is the application of OBAs.
The further "why" of OBAs was simple; with modern inventions and perfections of laundry/house cleaning products and appliances in theory Madame's laundry day/housework (or anyone else for that matter) should have been greatly simplified. No such luck. Product makers and their marketing/advertising henchmen went on a binge around the 1950's to convince women that now clean was just not good enough. You had to have a "whiter than white" wash or somehow you were a slovenly housekeeper who let down the team and was endangering your family.
Persons go on about bluing as if it was the bees knees. But good housewives, laundresses and anyone else in charge of that department knew a good wash done well needed the stuff nil to none. Again all bluing does is counter the yellowing of fabrics. If things were properly laundered, rinsed and ironed it went a long way to keeping them from yellowing.
In fact much of the yellowing you see (under arm stains, center of pillow slips and sheets) is caused by wearing things too long and not washing frequently nor properly. Either way all the bluing in the world won't cover up that mess. What you end up with is a darkly blue stained textile with an obvious yellow area still shining through. *LOL*
Sadly at least here in the USA it is very difficult to find laundry detergents, fabric softeners and even starches that do not contain FWAs. The American public overwhelmingly prefers "whiter than white" and "bright" colors that such chemicals give. At least in Europe you can find detergents especially for colors that do not contain bluing agents from P&G, Henkel and other top shelf products.
Why don't they do it? Dirty little secret is that for Tide and many other laundry products everything begins with one base formula. From there things are added or omitted depending upon which version is being created.
If you pull a MSDS for say Tide liquid detergent you'll see it covers almost every single version including "Free and Gentle". Things are just added or not included depending upon if is "HE" or "Total Care".