God is love… and God disciplines those he loves. Hebrews 12:6
Why do parents discipline their children? Love, they want their children to respect authority and do right. When they do wrong and choose not to follow their parents instructions that’s usually when discipline happens. Doing what a parent asks/says is biblical. Ephesians 6:1 says “Children, obey your parents in the Lord, for this is right.” 
When it comes to discipline some parents use/used a switch, belt, shoe, ruler, hand, etc to discipline their children. Some parents take/took away their child’s internet privileges, smartphone, car privileges, etc. Some choose timeout with the resulting effect. The goal of discipline? Teach, compel, inspire children to do what their parents say/ask. It is true some parents aren’t the best role models but many try to be. 
What about when we’re grown? Does following authority no longer apply? It does and even more. Some people say “I’m grown, I can do whatever I want.” That is somewhat true, in the moment yes we can do whatever we want but everything we do has an eternal consequence.
We aren’t grown to the point where God’s discipline doesn’t apply to us, He is our heavenly #Father and he disciplines those he loves.
God is love.