having the strip insertable may make the brightness-assumptions inside the device a bit more muddy. The idea is, that the environment is well-controled. People

having the strip insertable may make the brightness-assumptions inside the device a bit more muddy. The idea is, that the environment is well-controled. People inserting strips will, over time, put dust on sensors and LEDs. There goes your finely calibrated device and you're in no better situation than the woman outside a well-lit bathroom.