The issue, as many have stated, is that KSP is easier to handle than Orbiter. It took me several months to learn to use tools Orbiter. With Kerbal I was a few weeks and I learned the basics, except landings and rendezvous and manufacture airplanes. What attracts is gripping parts and assemble them to make the ship or rocket desired. It's addictive.
On the other hand too common thing is that in my videos many put comments like "looks like I used KSP" or "KSP is 1000 times better." For a while consider using KSP to make a video, but I did not attract much game environment presents. I like but as someone said, KSP is a video game and Orbiter is a simulator. These days someone asked me for help because wishes to Kerbal version of my video of the Martian mission novel Voyage.
Here in the forum, in another discussion, someone said if Orbiter implement the construction of KSP option would be the ultimate space simulator.