The waveform is audio at its most literal: a line tracing air pressure through time. DAWs draw one for every clip, which makes it the audio image every producer reads fluently, locating the drop by eye before hearing it.
As a live visual the waveform is the honest classic. An oscilloscope-style trace shows the actual signal, and different sources have visible personalities: sine bass rolls, square leads step, distorted guitar fills into a block.
Its limitation is what it hides: a waveform shows energy and dynamics clearly and pitch content barely at all. That is the gap the spectrogram exists to fill.