Most devs can't do SRE, in fact the best devs I've met know they can't do SRE (and vice versa). If I may get a bit philosophical, SRE must be conservative by nature and I feel that devs are often innovative by nature. Another argument is that they simply focus on different problems. One sets up an IDE and clicks play, has some ephemeral devcontainer environment that "just works", and the hard part is to craft the software. The other has the software ready and sometimes very few instructions on how to run it, + your typical production issues, security, scaling, etc. The brain of each gets wired differently over time to solve those very different issues effectively.