Two good reasons to talk to valuable friends about problems, neither of which are "unloading" or "venting" (which I agree is not helpful):
- seeking advice from someone whose opinion you value
- maintaining a networking of connections who care about each other doing well and know when one of their network is having a hard time

These are both action-oriented activities that prevent people from becoming isolated. Interestingly enough, a therapist provides neither in a genuine manner.