Is it ever wise to use "rem" all the time?

Wouldnt making

body{

font-size: 1rem; (default browser font-size)

}

and use everything based on rem make the website responsive and much more easeir to code? For some reason people told me that I should use em for font-size/padding/margins and rem for just general sizing like <divs> <li>,etc. Not sure why not just use rem for everything; since it reclaibrates to the user browser's font size. A clarification would be great :)

Epic visual tool

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