People who ride SRAM either use it because it came on their complete bike
I used 9-speed SRAM because I liked it more than Shimano- less finicky, better shifting feel, none of that orrible wooly “is the lever connected to anything” thing. And sure the mechs weren’t as well made but on the other hand, they still worked after they were wobbly and dented.
I use 10-speed Shimano because the first thing Shimano did when designing their 10-speed kit was to steal all of SRAM’s best ideas. So the shifters feel like SRAM 9, clunk click, and the cable pull is almost identical to SRAM. (but not quite! Because that would be too obvious). My Saint-on-XT set is a very moving homage to my old X9. (whereas 10-speed XTR still feels like 9-speed Shimano, ie, like it’s broken)
Course, you have to be mental to buy a SRAM groupset because it’ll have a Truvativ crank and Avid brakes.