Some people can indeed do what they need and want to do in six sessions or less. Some people solve their initial problem in a few sessions but then decide to spend more time to resolve some others, or come back for another problem at another time.
Some people decide to do long term psychotherapy.
For many people long term therapy produces a substantial net financial gain, most often by increasing earning power, improving physical health, or making a functioning marriage possible. The gay and lesbian clients I have worked with have been happy with the results, although I am straight. However, I did recently refer a gay client to a gay counsellor for supplementary work, because I felt he would benefit from a gay male role model and detailed information about the gay dating scene in Toronto. Good psychotherapy is empowering, though it might disconcert a Rock of Gibraltar type by getting him in touch with his need for emotional support. Sometimes also an inadequately trained therapist will unconsciously foster dependency for his own gratification.