Deadlifts, one of the core exercises of SS, is famous for improving posture when performed correctly.
Lifting weights in general has been shown to improve cardiovascular health; obviously not as much as pure cardiovascular training, but the science is pretty conclusive that it has a positive impact on your heart.
Lifting weights prevents injuries by improving bone density, strengthening connective tissue around troublesome joints (knees, rotator cuff, hips, etc.) and preventing the use of poor posture to accomplish everyday tasks (e.g., instead of hunching your back and stressing your spine to carry a heavy ice chest, you can use the muscles of your upper back). It also adds muscle, which increases your BMR (AKA metabolism).
If your main interest is in gaining muscle and looking better, there may be better routines. But Starting Strength is about one thing ... strength. Pure and simple. It never claims otherwise.
Starting Strength has been used as a fundamental building block by athletic trainers for years; it is often modified to be sport specific, but its fundamental lifts have proven effective over and over. After one has reached strength standards, it is typical (and recommended) to move on to a more advanced strength routine, which may explain why many of the big guys you have met are no longer doing a stripped down strength routine.
Yes, those with serious pre-existing injuries may want to opt for a different program (probably machine based), but that will be true of almost any strength training program. Those with only minor injuries can just start SS at a lower weight and improve more slowly.
Hope that helps address your concerns.