Celebrity endorsements and luxury brand development almost works hand in hand. These brands nowadays seem so reliant on celebrities to act as a spokesperson/brand ambassador. Just look at red carpet events, where celebrities are drenched in jewels and glamour, each and every one of them becomes a walking billboard.
In my opinion, endorsing a celebrity feels like brandings easy way out. Seems like associating with a celebrity is the easiest way to build a brand. I’ll have to look into my assumptions. Some reading materials I’ve come across so far here and here.