blockchain – Why must the entire chain be included in calculations if it’s already been validated. Why can’t the validated portions be archived to save energy?

I’m new to this so don’t laugh. If all of the previous transactions in a blockchain have been validated as authentic, why does the entire chain have to be carried forward in the calculations? Why can’t the validated portions be hashed and archived to save energy costs from handling so much historical data. When accountants calculate the current years income, they don’t go back to when the company started and add up every income and expense item, they just add the current years results to the archived past totals. What am I missing.