People are the ones who like boxes. They want a black and white set of rules so they can "please" God by standing exactly right according to those rules.It's man that gets boxed...if we allow ourselves to be....the Enemy likes us to have ridged thinking. In fact, as I think on it...most religions and controlling systems demand boxes. They are and have always been afraid of free thinkers...afraid we may come to the knowledge of The Truth .
Probably most of the natural Israelites in the wilderness usually obeyed the letter of the law [613 rules] as God gave them to Moses. But, how many did they need to disobey to displease God? So they asked for and received atonement [temporarily?] when they broke a rule, but while there was atonement provided for accidental or ignorant disobedience of those laws, the punishment for intentional disobedience was usually death [often by stoning]. They thought they had the rules in a box, but God really did want more from them than the 613 definitely described rules. David clarified what God really wanted here:
"O Lord, open thou my lips; and my mouth shall shew forth thy praise.
For thou desirest not sacrifice; else would I give it: thou delightest not in burnt offering.
The sacrifices of God are a broken spirit: a broken and a contrite heart, O God, thou wilt not despise." Psalm 51:15-17
God has not changed in spite of the differences between that covenant and the one available through Jesus. But, people still want to receive all of the rewards and so try to obey the letter of the rulebook [the Bible] while allowing garbage to dwell in their hearts and even feeding that garbage. If this only spoke of unbelievers, it would be sad, but we know that too many who carry the label of Christian feast sometimes [if not always] on more garbage than on the flesh and blood of Jesus.
We know the result of their failures in the OT. Of the 600,000 men who were led out of the slavery of Egypt, only two made it into the Promised Land.
They could not make it by only following a black and white set of rules and neither can we. We really do need to be able to recognize His voice and to obey it. Many who read the Bible will hear Him as they read, but too many do not... even they are also called Christians
"Not every one that saith unto me, Lord, Lord, shall enter into the kingdom of heaven; but he that doeth the will of my Father which is in heaven.
Many will say to me in that day, Lord, Lord, have we not prophesied in thy name? and in thy name have cast out devils? and in thy name done many wonderful works?
And then will I profess unto them, I never knew you: depart from me, ye that work iniquity." Matt 7:21-23