It's not reciprocal, which gives you a feeling of vulnerability. Maybe? Also for ppl who are too proud to admit they need help or other people (heh like me), transference brings up a whole bunch of issues we'd rather never saw the light of day. Also perhaps a fear of rejection or abandonment.... that we know the T doesn't feel the same way, and that they may reject us or not agree to see us, if they feel we as clients are too attached.