There is a saying: "Music is it's own reward." Its not quite a labour of love though; musicians at all levels are earning a living, partly touring, streaming and sales, partly from licensing of their work.
The PRS (Performing Rights Society) and PPL (Phonographic Performance Limited) handle the licensing data; both actively inspect all types of public spaces. When they discover you have been playing music without the correct licences and without reporting usage, there are fines and / or estimated charges, which can be retrospective and significant.
The PRS (Performing Rights Society) collects and distributes annual licence fees from the public performance and broadcast of musical works, for each “venue”, where you have music playing.
PPL (Phonographic Performance Limited) is a music industry licensing organisation that collects and distributes airplay and public performance royalties in the UK. This relates to reporting usage.
(NB: During March/April 2018, The PRS and PPL will form a new joint venture called PPL PRS Ltd. The two parent companies will continue to carry out everything else they do separately, other than public performance licensing.)