I started my sentence with “In my case, …”, which means I was speaking only about my own preferences, not something universal. But you did ask why someone would choose SRAM over Shimano, and I think ergonomics and 1x vs. 2x are two good reasons. I wanted my next road bike to be 1x and I vastly prefer SRAM’s ergonomics on dropbar bikes. Other people prefer GRX STI levers to Ultegra or DuraAce STI levers. My point is simply that ergonomics and gear choice are factors, not that everyone has to agree with your or my choices.
Even then I don’t think Shimano’s cassette has tighter gearing. SRAM offers you one more tightly spaced gear at the top end at the expense of one more large jump on the climby end. Shimano and SRAM made the same tradeoffs with their 11-speed cassettes, too. (Even when I had a Shimano groupset on my previous road bike, I did replace my Ultegra cassette by a Force cassette.)
Sure, and I am not a SRAM zealot. I’m very happy with my XTR drivetrain and XT brakes on my mountain bike 
Is there any word whether Shimano will still only offer the few gearing options that are rumored? Is there talk of a GRX 1x12 cassette for gravel riding?