You don't want your released game to crash in level 11 if the player happens to look behind the wrong lightpole because a texture is missing, but you do want to notice that in development.
But with that said, we didn’t generally crash the game due to a missing texture, even during development, as that’s a super common problem which would have impacted development too much; instead, we just drew anything which used a missing texture in max-saturation pink and green instead, alternating between the two colors once per second, to make sure it’d be super visible to anyone looking at the game during development.
We did usually change that behaviour to instead render missing tetxures in alternating black/near-black instead of pink/green for our final releases, as that was deemed a relatively safe change.