Why cover nesting boxes?

[flrn]

I am new to chicken keeping, and have seen pictures of coops with the front of the nesting boxes secured with hardware cloth, inside the coop which prevents the hens from getting into the nesting box. Why is this?

 

[Chickmagnet36]

Mostly to prevent them from sleeping / pooping in them. Once they get used to using the roosts to sleep, and get close to laying age, the nest boxes can be opened up for business.