The device shown is similar to a Sony Walkman mobile audio tape cassette player
At the time of the Walkman's release in 1979, the audio tape compact cassette was an established standard for stereo music distribution, otherwise to play your own music, you had to deal with bulky non-portable LP record players, cassette decks for hifi racks, or portable boomboxes with handles, or even bulky 8-track cartridges with even bulkier players.
The Walkman, a new class of audio playback electronics that you could put in a (big) pocket, was revolutionary.
Sony's advertising campaign portrayed the Walkman as for active, hip and cool people: https://stereo2go.com/forums/threads/the-first-walkman-ads.4479/ https://music.si.edu/video/iconic-sony-walkman-1979-tv-ad Much like Apple's "silhouette" ad campaign for the iPod music player
Also, the Walkman style headphones were lightweight with sponge foam ear pads and small 3.5 mm plugs, vs the then-standard 1/4 inch/6.35mm stereo jack.
Much lighter and cheaper than the priorly typical headphones with bulky vinyl-covered earpads with bulky cords and jacks, as would be used in professional audio setups today.