Racing engines use forged steel crankshafts. OEM crankshafts are often investment castings. The simple truth is 2000 HP engines would not use investment casting in no way way, shape or form. Forgings are stronger no matter how you slice it. Same goes for forged race wheels and so on. Investment casting is a superior method over sand mold casting by far. However, it will never equal the strength of forged steel. We can argue the subject all year but the simple truth is forging yields a stronger product. If Nascar engine crankshafts were made of investment castings they wouldn't make it two laps. They would snap like a twig. They will take high RPM's for very short spurts but won't hold up to sustained high RPM over a long period of time.
I'm not disagreeing with you on the additional strength forging adds to any steel. It takes a below average steel and makes it average, or an average steel and makes it superior. In your NASCAR example it's taking superior steel and making it more-superior.
But the real question is 'what are the requirements?'. Smith K frames are limited in the amount of 357 Magnum they can handle in their forged frames, while the cast GP-100 can run them all day long. In this case the cast gun is stronger than the equivalent forged gun, although to be fair the GP is slightly larger than a K frame.
And there's plenty of handload recipes that are only for Rugers cast guns, and will blow up a forged still frame.
I would certainly argue that Rugers investment cast steel frames are more than strong enough to stand up to constant use in a 1911. A major company like that wouldn't skip durability testing on a new design.
Using forged steel for a 1911 simply means you can use lower quality steel and still get the 'good enough' results you need. I'll guarantee that's what Taurus is doing, and if I remember Springfield gets their 1911s from an overseas company as well. Ruger can simply start with the strength steel they need and start the manufacturing process from there.
At the end of the day I'm guessing it's personal preference though. I doubt any of the major manufacturers have any questions about what strength steel to use in 1911 frames and slides. It's a 100+ year old design so there's nothing in it that's still a mystery. And they all will have to support them for years, so I doubt they would put themselves on the hook for future warranty claims using sub-par materials in a major component.