Allowing oneself to be bored, or at least idle, without self-judgement, can be extremely valuable. You're likely processing things in the background (often without realizing it), which will make your active decisions and activities easier.
A lot of my shower time is “free range boredom” where I just think about anything. I really enjoy both of these things.
All three have the commonality that, traditionally, you’re not disturbed and you can think at a relaxed pace.
On the other hand, I miss taking showers without muttering to myself.