I have worked in workshops with massive machine tenoners large enough to cut both sides of the tenon on an 8″ x 12″ beam in one pass and it comes out perfectly parallel with shoulders perfectly square ever time. Truth is that I really detested the whole set up thing and the separation from my work caused by the machine.
Making these tenons is hard work by hand, but I like hard work and I like maintaining my body through work, especially as I grow older. Here you can see the tenon fully fitted into the mortise and the two of us hanging either end pressing it together. I like working and I like wood so working wood means a lot to me. It’s real wood working.
It’s not a nostalgia thing at all. It’s the senses touched by real wood, the essence emanating from the newly opened cells, the flex of the long paring chisel (most woodworkers know nothing of) and the sound of the mallet striking the chisel. Real wood working. That’s why I work wood this way.