As a PPL and PRS member - even if your clients play the music so other people 'consume' it, then as the dirty deed is done on the business premises, the business needs the licence. If they wear in-ear headphones and nobody else hears it - staff or the public, they don't.
PRS do not collect money for every release, and nowadays, many people put their own music on the net for streaming and are NOT PRS members. This can be played trouble free - from PRS's perspective, but how would you cope with somebody playing their music in the gym, and perhaps videoing it being played, then slapping a bill in for the copyright payment. They're still entitled, even without PRS involvement. Signing up for PRS means you point them towards PRS, and PRS will have a teeny payment for them in a few years maybe.
With the blue stickers displayed, you just forget music.
You could only play rights free/rights paid music - it's easy to get nowadays and you tell PRS when they ask that only rights cleared music is played in the venue. It's very common for touring shows to warn theatres that no PRS controlled music is used in this production, to avoid the theatre deducting PRS payments from the settlement. In theatre, they pay a percentage of the box office to PRS - let's say the rate has been agreed at 2% - and the show is half music and half chat - they then pay 50% of the 2% to PRS. PRS can also (but rarely) require a venue to itemise every piece of music played. Who can afford to have a member of staff monitoring the music played?
Far more economic to just say fine - give me the licence and add it to your other business expenses.
People always groan about PRS, but like a TV licence, it's just simpler to pay, than fight and probably lose in court. The facts are very simple - consuming music requires paying the creators. My chiro office have paid for copyright free background music. They don't pay PRS, but somebody else - and the music is nowhere near the quality, and type customers would actually choose themselves.
I'm now ancient, but my PRS payments go up each quarter. When somebody knows a certain piece f music is going to take off - they can if they wish, remove the music from PRS and deal with it themselves. They then have to work damn hard to tie down the people using it and deal direct - and that is a real pain. Many wish they hadn't bothered.