My suspicion from regular use of ear plugs is that the wax sticks to the plug every night. I use a new set every night. Pretty wasteful, but man, I need my sleep.
But now I'm the one using them. Haven't done as much work researching earplugs as some posters above, but like the Loops. For comparison, I have earplugs at work, that feel like someone was raping my ear every time I'm putting them on.
So, there's definitely earplugs and earplugs. If you need to use them, might be worth few hours and few bucks spent on testing/research.