There are many benefits to psychotherapy. Although other modalities can provide support and solutions to life's challenges, psychotherapy offers it's own unique contribution to health, well-being, and personal growth. Often times it is a useful or even an essential complement to medical care, body-oriented therapies, and spiritual practices. The tool in psychotherapy is the relationship between client and therapist. Many of life's difficulties are relational in nature. It makes sense that relational problems can be transformed within the context of a therapeutic relationship, where important boundaries are maintained that allow for these relational shifts to take place.
In addition, psychotherapy is much more than "talk therapy". Language is a primary tool for giving structure and meaning to what can otherwise be felt as vague impulses, perceptions, and experience. The verbalization of feelings, experience, and memory allows for greater internal regulation of feeling states and more effective engagement in the psychological work that affects all areas of functioning. One's experience once known and expressed can be integrated and transformed through dialogue. In addition, there is a wealth of current research on the brain that shows how relationship (non-verbal and verbal communication, eye contact, emotional attunement) affects brain development and neural pathways over the life span.
There are many issues that bring people to see a therapist. The following list includes issues I have experience working with:
Depression   Grief and Loss
Anxiety   Work-Life Balance
Life Transitions   Wellness and Self-care
Relationship Problems   Cross-Cultural Understanding and Communication
Living with Illness   Step Parenting and Stepfamily Dynamics
Preparing for Surgery      
The client's participation is just as important as the therapist's skills. Benefits can include symptom relief, increased self-worth, self-respect, and self-acceptance, increased autonomy and flexibility, improved relationships and job satisfaction, clarity of purpose and life meaning, inner peace and freedom, and greater self-awareness.