spoiler
alt text: A two panel comic. In the first panel there are two buttons labeled "I don't believe in prescriptivism" and "'Literally' cannot mean 'figuratively'". A finger hovers between the buttons. In the second panel, the finger's owner is sweating and wiping his brow, unable to decide.
No one ever seems to have a problem with really (as in real) or very (from verily, ie true) being used in figurative senses, however.
I'm not saying English is perfectly consistent or that its never happened before, I'm saying why introduce ambiguity that gains nothing? Do we truly not have enough very/really analogs?
That's because they're words used to provide emphasis in the same sense as the original word.
Very and verily are similar. I'm very tired, or verily I am tired. Maybe one is used more to say "to a great extent" and the other to mean "no kidding", but they're roughly the same. Same with truly from the root same root as "truth".
What makes "literally" vs. "figuratively" annoying is that literally used to mean "not figuratively", but is now used to emphasize a metaphor or a comparison.
So, "it's literally 5 tons" could mean either it's actually 5 tons, or that it's very heavy but probably nowhere near 5 tons. If someone actually wants to say that it is actually true that it is 5 tons, the worst word they can use to emphasize that truth is "literally".