Well...if the therapist encourages it, the therapist.

I can see scenarios in which a therapist doesn't encourage it at all - like I can't see No. 2 encouraging dependency at all with her remote attitude - but it develops anyway, due either to the fact this is the client's closest relationship with anyone, or this is the way the client develops relationships as a matter of course. Not sure it's the client's fault then in either scenario, but I don't think it's the therapist's either, except insofar as they chose their career path.

The only thing that is definitely the client's fault is if they act out their dependency issues in some extreme way, like harassing the therapist outside of the office. Some will argue it's still not the client's fault then, but anyone who is an adult should behave as an adult is expected to behave.

As for me, I blame society.