Many people find the easiest course of action is just to do what they did yesterday. Doing something different has downsides:
- it may mean breaking a habit. My wife and I joke about my driving on autopilot. If it's Friday I turn right, turn right, turn right, then turn left and we're at the glass recycle place. Varying the pattern means a conscious effort to decide to make a different turn.
- it may require a decision, and the decision may require researching an issue and getting information.
- it may mean risks, unknown risks. Doing what you do you're very familiar with the risks you run, and you're comfortable with them. Doing something different means you're less familiar with the risks, which can mean you become nervous and tense, not something one likes.
- there may be unintended consequences.
So one part of conservatism is just an extrapolation of our habits.