A "phone" these days is usually, more or less, a small box with one glowy side. Yet these self-same devices, to represent "phone", use the silhouette of the handset from an old Bell Telephone landline model, thirty years after those phones went out of fashion. To even the younger generation, that shape
means "phone", even if it doesn't look like a phone.
Similarly, the D-pad from a NES controller -- or worse, an Atari 2600 joystick -- is often used to represent or signify "video games".
"Home" is based on tract housing from the 1950s; yet even if home to you is an apartment, condo unit, palace, or boat, that icon still means "home".
There's another example. I just recently bought a Moleskine with an abstract graphic image of an audiocassette on it. There's no real reason for this; it's very hipster. It's sort of "celebrating the audiocassette" because to an entire generation of people, the cassette -- and its shape -- meant music (especially music on the go, like in a Walkman). Youngsters connect to it too, in a "retro" way. The same will be true of the floppy disk icon. No one uses it now, but it was ubiquitous that -- like the audiocassette or the distinctively shaped horn of a Victrola phonograph -- its shape has become semi-permanently associated in our culture with its intended use.