Question about summoner names

So I just found out all the summoner names that are champion names aren't available to anyone. They're all level 6 and owned by Riot or whatever. I had asked riot if I could have the name "Lulu" as it hasn't been used in years and was level 6 etc. They said it's against policy and is a security risk. Any idea why? I'm curious now!

Search any champ name, they're all level 6 with 0/476 xp haha