Why do breeders do this?

[EdgesideHomesteadTX]

I also use color zip ties along with a toe puncher and I'm breeding quality byc and I'm probably as serious as a game breeder about my stock and hatches I'm waaay into it!! And with the several breeds I have it makes it quite easy to tell the chicks apart except I have 3 different lines of new hamps and so with those I just mark them different colors and different toes