I work in an aerospace company, and there's a lot of engineers here, and other scientists, who got their hands "dirty" in actually building and testing some pretty complex and advanced stuff also. Sure, there are also technicians working and other people, but when you build something that wasn't ever built before - and maybe will be sent where "no one has been before" - technicians are not enough, and you can't just send them blueprints, and hope for the best.
On the other end I've met IT engineers just out of uni who believed they were being hired to lead a team of several developers, and they would just "design and instruct do to".... just to find they knew less of many "technicians" working there. Actually, in IT you do expect engineers to build parts of the systems, especially the critical ones, because, especially in software, every product is actually a prototype. The "production" part is just sending out copies to be installed.