When I was young my head was always under the hood of a car. I spent many a night working underneath cars as well. Now days you have to dig through shrouds, covers, countless hoses, turbo's, connectors, sensors, large plastic tubes, gizmo's, and wtf's just to find the engine so I mostly let the "new" young guys handle that when needed.
Mostly, as I've aged and become somewhat arthritic and stiff I simply can't reach the parts on the engines. Pick ups are a good example, they keep making them larger and larger yet the engines are made smaller and smaller. More HP and torque but dimensionally smaller engines that are hard to reach sometimes.