You're quite right. I'm an ex-Googler and SRE was the last thing I did at Google. As a first-and-foremost programmer I was bored out of my wits and frustrated by the fact that while I was writing repetitive monitoring rules actual development was happening somewhere else and I had little impact on the design of the system. Granted, a lot of folks over in SRE loved it but I would venture to say that most of them were much closer to being a sysadmin than programmer. Folks like myself tended to 1) move to SWE, 2) quit and 3) some endured and became managers over time.