That is a good point, when I started sleeping with earplugs at my parents house where I don't have a fan or some noisemaker it made a huge difference to me. I found I would fall asleep much faster even when there was no actual obvious noises to keep me up. I've noticed when I'm falling asleep even minor noises can 'jolt' me (its the best description I can think of) and effectively reset my progress of falling asleep. Putting in earplugs can cut my time-to-sleep in half when I'm away from home.