That was a big part of my decision.
To me, I'm more focused on Technology/Engineering but I wanted to allow a wider audience and STEM was a much better fit than "TECH".
That being said, I plan on doing more with SteemStem.
SteemSTEM of course supports content on technology and engineering, we have had good authors in this area, the difference is that SteemSTEM standards are different. The main idea as @lemouth says is to make possible the communication of science in Steem.
I'm a big fan of science, I just didn't want to focus on that. To be honest, I'm more of a technology person with a touch of Science, Engineering, and Math.