I usually keep the original unless it’s specified that I have to turn over the original. Although, if not specified I might keep the copy for myself, it really depends what I’m signing and doing.
There can be multiple “originals” in some circumstances. Like when you sign closing papers when you buy a house, you sign two of everything, sometimes more, so all parties have originals.
As far as the IRS they require originals fir some things, but will take e-filing for other things. I assume eventually the IRS will let go if requiring originals for anything.
Many institutions require “original” birth certificates and death certificates. You can buy multiple originals.
More and more original signatures are less important. That’s different than original documents provided by a government agency.