Distance learning may work for subjects that don't require hands on learning - such as law.
Engineering, hard sciences, medicine - and yes, plumbing, electrical, HVAC, and auto mechanics - require extensive, guided hands on work in laboratory environments. Universities provide these to students preparing for careers in engineering, medicine, and the sciences. Community colleges and technical institutes provide these to students preparing for careers as technicians in industry.
And the classroom component of these curricula needs interaction between students asking questions and instructors who answer them - and provide help for students who don't get it on the first try.
Be careful about throwing out the baby with the bath water.