Why should you change up your exercise routine?

In general, to avoid adaptation, you should change exercises once every 3-5 weeks. Make a list of exercises for each body part and simply pick a new exercise every 3-5 weeks. This will go a long way in helping you make
consistent progress.

Found this in the web, hope it helped a little, based on my experience, I feel like we should change it because if we stay on the same routine, we might not see progress

Ican only answer your first question, a machine is like a human body because it's a little similar. they both almost work like the same.