Nathan, That's really not true and kind of an outdated perception. Think of technical consulting and engineering firms like PR and advertising agencies. The head of these agencies usually have experience germane to its service, be it account people or creative.
Corporate engineering departments like rocket manufacturers, software companies and electric auto manufacturers (the companies of the leaders you cited) are becoming smaller and more marketing focussed. Even concept design and feasibility is becoming increasingly contracted out. Not just everything after 30 percent design, where details use to be designed and engineered by contractors.
Successfull corporations that want to keep most work in house, don't have too many layers of communicators and send its engineers to charm school.
Most technical consulting, engineering, construction and manufacturing support is being done through contractors these days. Corporate engineering departments have become or are becoming engineering management. A really good example is oil and gas companies and utiltities. Most major oil and large utilities contract out almost all its engineering after initial desire. The head of those contractors are usually engineers, scientists or someone that really knows the nuts and bolts of the activity or product. They have to bring in clients to justify higher salaries above engineering grade.
For instance, Shell contracts out R&D, exploration, production, transmission, refining and marketing of oil and oil products. AMEC for technical consulting. Schlumberger for exploration. Halliburtan for drilling and production. Bechtel for production and refining. WorleyParsons for refining modification and routine operations. All of these examples include technical consulting and engineering. Everyone of the employees of these contractors are trained to be client focussed (i.e. salesmen). How much selling they're doing depends on what they doing. Sometimes it's 1% or the time. Other times it's 99%.