There is no single answer to this question. Whilst many people live alongside the voices they hear in peace (and may find them a useful or meaningful part of their lives), many also struggle to cope. This can be for many different reasons, including:
The voices/visions: content (the things they say or show), identity (who the voices/visions seem to be), intensity (how loud or frequent they are) and how much energy is expended in dealing with them.
Others’ responses: Sometimes it’s not so much the voices themselves that is the problem, but the way others respond to them (or how the voice-hearer fears the others will respond). This can lead to people isolating themselves or ‘wearing a mask’ to hide and important part of their lives.
Context: If someone is in a work/home/study/social context where they are being bullied, demeaned, marginalised and/or excluded, this can make it harder not to listen to critical voices (and leave the voice-hearer feeling depleted). Sometimes people find aspects of the environment can be problematic – e.g. sensory overload from being in crowded and loud spaces and harsh lighting. Some people find their voices get louder or more challenging in certain situations – physical, relational or emotional.
Emotions: If someone is struggling with part of their history and/or emotional life (e.g. feelings of anger, shame, grief, powerlessness etc) this can be reflected in the voices someone hears and, equally, make it harder to respond to them. Voices can, for some people, poke very sore spots.
These are just some possibilities – there are many more. Sometimes, if a person works out what might be making the voices so unmanageable they can find strategies that help ameliorate that.