Why do rules and laws change?

That was a question on facebook today.  Why is it that today it is okay for people to do things that we were told was a sin 20 years ago.  Well, the way I see it is that we have laws and bylaws.  A law would be something that is set in stone that is a matter of life and death, Heaven or Hell, what we must do or not do in order to be saved or lost.  A bylaw to me would be a custom or guideline to set us apart from the world.  ie.  to distinguish us from another sect or culture.  For example I am Pentecostal.  I have been raised to not cut my hair, not to wear that which pertaineth unto a man, etc.  We didn't go to movies, watch television or a number of other things.  This kept us to be untarnished from the world.  They were not fences to keep up shut in as much as they were fences to keep the world out.  Today many Pentecostals cut their hair, wear make-up, woman wear pants, etc.  But to say they are doomed for Hell is not my place to judge.  I, on the other hand, am proud of my Pentecostal Heritage.  I am glad that people know when they see me that I am Apostolic Pentecostal.  It is a identifying factor much like a team uniform or dress of a culture.  We know the Amish by their dress and ethics, the ball teams by their uniforms, etc.  For me to change my appearance to one that blends in with the world would not be me at all.  I am who I am and comfortable with it.  I feel that God is pleased with my decisions to keep the Pentecostal Heritage alive and well.  I raised my daughters to hold fast to the same teachings and they have never bucked against it.  My way of thinking is if you desire to wear pants or cut your hair you might as well do it, as it is the heart that God judges and He said that if a man looketh upon a woman with lust in his heart that he had commited fornacation with her already.  So, it isn't the outside of the cup that defiles a man (or woman), we could look the part and be full of sin inwardly, but if we are cleansed inside, then we should want the outside to look Holy as well.  It is our responsibilty to search the scriptures, for in them we think we have enternal life.  And we are to seek out our own salvation with fear and trembling.  I know that in that day, I never want Him to say "depart from me you worker of iniquity, I never knew you", but I long to hear those words that thrill my heart just to think of them, "Well done, my good and faithful servant!"    To God be the glory!!!!  

Thank God for His love and mercy and for allowing me to have another day.