20 years ago that may have been the case, as live music photography was primarily used for album covers, fan merchandise and press marketing.
Now any band, duo or solo performer can have their own Social Media page and free website, making self-promotion not only possible but an essential part of marketing yourselves to potential venues and getting people to your shows.
However live music photography does come with it's own special challenges: lighting that alternates between almost none to dazzling, subjects who very rarely stay still for long enough to allow a long exposure time, the inability to use your flash, positioning so you can get great shots without putting off the performer/s and negotiating an audience.
It is the offbeat photos that help to convey the energy and atmosphere of a gig, such as the reactions of the audience or the looks between the musicians (especially when one has just 'gone off-piste'). I not only have lots of experience shooting in low light conditions but have also learned to pick up on those little cues on stage to know when a great shot is just about to happen.
Note to Venues:
Having a photographer capture the live music events you hold is also a great way to promote your 'Gig Nights' and can be tailored to focus more on the audience and the great time they are having!