Words describing the pat acceptance of a thought or practice simply because "that's how it's done."

Solution 1:

While your question and its focus is slightly different from previous questions 28866 and 51451, some of the answers to those questions apply here. I'll mention those below, but first here are some words that were not mentioned in the previous answers: ovine, staid, stodgy, complacent, traditional.

• ovine - Of, pertaining to, resembling, or being a sheep.
• staid - Always fixed in the same location; stationary; composed, regular, sedate, steady
• stodgy - dull, old-fashioned
• traditional - Observant of tradition; attached to old customs; old-fashioned.
  [also see conventional, customary, establishment, orthodox]
• complacent -
  Uncritically satisfied with oneself or one's achievements; smug
  Apathetic with regard to an apparent need or problem.

For question 1 regarding "words to describe a person who thinks or behaves" in a "that's how it's done" manner, answers to question 28866 mention close-minded, obstinate, dogmatic, narrow-minded, incurious, uninterested, uninquiring, uninquisitive, indifferent, parochial, provincial, Luddites, willfully ignorant, stick in the mud, philistine, stubborn, old dog, unteachable, ignoramus. It also mentions one of Monica's suggestions, hidebound. Answers to question 51451 mention some of the same, plus blinkered, obsessed, tunnel vision, locked-in, myopic, navel-gazer, self-centered, ostrich.

Several of the words mentioned above, indeed probably most of them, can apply to question 2 as well. But it's difficult to come up with phrases without knowing more about rationales; whether fear of the unknown, fear of schedule problems, self-knowledge of one's abilities or of co-workers' abilities, stupidity, brilliance, ... the scope is so wide open that that part of your question may not be answerable.

Solution 2:

A person who acts without analyzing could be said to be uncritical.

One who does what has always been done, without re-evaluating traditions in the light of new information, might be hide-bound.

Solution 3:

A word which got short shrift in the answers above but goes to the heart of the question is "dogmatic". It means done according to dogma, or received truth, without any independent thinking. It can be applied to either the person or the action.