The streaming platform does not matter. You can use anything you want. Its the actual act of playing music that often requires a licence depending on where you are. I live in a scandinavian country and have to pay a fee depending on the store size. 100 square meters would cost $60

(Interestingly i subconsciously converted to $… if you’ve worked retail in a tourist destination you must have heard ‘how much is this in dollars?’ but not really the same question for any other currency

Not from US, but from my observation these are the most commonly used music sources used in stores

Spotify - Good if you want customised song selection, playlists could also cover if you want similar songs to previously played songs.

Radio - Good if song licensing is a problem around wherever you are. Internet radios of specific genres could do the trick for you too.

YouTube- Good if you want large song compilations. You can find all sorts of “1 hour of (insert genre here)” videos all around.

Why do they think it’s necessary to fill every area with music

It should be ok for places to be quiet. If employees want music they should wear headphones. That way they could listen to what they want too.