First I'll say that I wouldn't listen to the advice or hang on the word of just any therapist or pdoc. I've had experience with some whose advice I totally ignored and had to seek out other opinions.

I think some people have problems that are beyond the scope of what they can handle themselves and don't have a support system to help through difficult times. I think a T is the best resource to help someone get their life back on track when they don't have any other resources, or they've all been used. It can be so helpful to hear an opinion that is not based on emotion but on pure objectivity. Even when the advice a T gives isn't rocket science, a good T can communicate it in a way that others can't when emotions get in the way.

I tend to think it's similar to criminal law and why there are lawyers who handle cases. If criminals were tried by family members of victims, imagine what would happen. Some wouldn't care about the accuracy of the facts at all they'd just want revenge. So you have a lawyer who has no emotional connection and is able to clearly analyze the evidence/facts as they are presented. I know it's not a perfect system but that's the intent at least.

In therapy, the T doesn't know you, so they can offer advice based soley on the information you provide and nothing else. This is a pretty unusual relationship- to share the deepest secrets with a person who has no emotional ties and can see from an unfiltered viewpoint. Of course this seems to change over time, so it's never a perfect science. Still I think it does serve the purpose pretty well and helps a lot of people. Also because they've had an education in the way the mind works and experience with a lot of people who've been in similar circumstances. So, they've seen what does and does not work. Often times the most effective solutions to problems go against one's natural instinct and you wouldn't even think to try the simplest things.

As for reassurance, until my most recent experiences with my pdoc and T, I've never gotten comfort from a T telling me everything was going to be ok. If I felt depressed, I felt depressed. As a child I looked to my T for adult guidance in a sense since I didn't get much at home, but that is a totally different therapy relationship. Children need models so if they don't get it from home, therapy or therapeutic programs can help provide that. Now as an adult with issues like social anxiety, ADD, maybe a little Asperger's, I look for reassurance that I am handling things in my life well - as a parent, a student, a professional. But that's because I've never had help with a lot of these skills until now, so I look to them as a mentor in an my areas of weakness. But I am very specific in what I seek out from my pdoc and T since I am lucky and have a great support system of friends to turn to. I believe many people do not, and to them their T becomes the entire support system.