Because your friend may be too close to your problems to be of help, may not speak with candor to avoid harming you/your relationship, may be an active particip

Because your friend may be too close to your problems to be of help, may not speak with candor to avoid harming you/your relationship, may be an active participant in your problem, may have no experience talking/thinking about your problem limiting their ability to offer useful feedback… Without even broaching the diagnosis and treatment of mental health conditions, there are any number of reasons why paying a neutral third party to discuss your problems could be preferable than talking to a friend at a bar. Nor are they mutually exclusive.