Why do people lay hand mirrors face down

I always thought you should lay a vanity/ hand mirror face down/ mirrow side down. I was wondering if there is a reason for that or if anyone else has hear this. If they have why should you do it?

I personally believe that you should lay a mirror face down. The reason to this is if it were to be on a floor. If you accidentally step on the mirror, then no damage would be done to your foot, however; the mirror could have broke. It might still be in one piece though, depending on how strong it is. If you were to have a mirror faced up, and you step on it; then let's just say that you wouldn't like shards of glass in your foot. Placing your mirror, faced up or down is your own preference. The way you place an object won't lead people to thinking things about you.

For me:
1) mainly to keep dust, etc. from landing on the mirror surface and getting it dirty quicker,
2) because the back side has really pretty monogramming and engraving so when it's not in use it's nice to see the decorative side on my makeup table,
3) when I pick it up, it's more natural for me to rotate my wrist inward to use the mirror side.