A squat bar is not as versatile as a safety squat bar which you can use for safety bar squats, Hatfield’s squats, lunges, good mornings it's a lot more versatile than a squat bar which is predominantly made just for the back squats.
Also, if you have limited shoulder mobility, safety squat bar puts you in a more stable place. Where the squat bar is straight, comes without handles or pads, and looks like any other barbell.