You better not look up the ISS pictures ...
When something is not 100% known to not fail, you want the wiring accessible. This means any late-stage modifications are done externally.
Also, once you certify some system/box, you will not be adding stuff to it. It is safer/more reliable to just not touch the certified box and pull the wiring externally. This is normal. It is not a spaceship .. set .. but an actual spaceship.
Yes, you want as much as possible tucked away ... but that 'as much as possible' is never 100%, if it is, it means you left potential capability on the table. At least that is how I always understood how this went. Reparability>Reliability>>Convenience>>>Looks.