Yes but most people don't have large deployments like Netflix. The main reason Neftlix and co build entire images is because if you're scaling up and down by thousands of instances then the extra time for those instances to do all the build, configuration and so on is material. So you're better to do it once and essentially CTRL+C CTRL+V.
If you're only scaling up a few instances at a time then your number one consideration is probably making life easy for yourself.
If you're only scaling up a few instances at a time then your number one consideration is probably making life easy for yourself.