"The high priest has the highest rank of all the priests. The anointing oil has been poured on his head, and he has been ordained to wear the priestly garments... He must never leave his hair uncombed or tear his clothing. He must not defile himself by going near a dead body. He may not make himself ceremonially unclean even for his father or mother..." Leviticus 21:10-11 (NLT)
The point of the text is that God expects more of leaders, especially His leaders. The higher the priesthood, the higher the expectations of purity. Their lifestyles had to be different. Their purity had to be superior. Their humility had to be their mark. They were expected to sacrifice their comforts for the sake of the people.
1 Peter 2:5 says that we are now "his holy priests (or holy priesthood)", speaking of those who know and follow Jesus Christ. He now looks at us as His representatives, and high expectations of character comes with that.
A great reminder for those of us who desire God to use us for great purposes. The higher the leadership, the higher the expectations of character. That is why Jesus is the ultimate High Priest. The roots need to expand before the tree grows.