Handing a patient a tissue breaks the thought that the patient is processing. This is also why most T's do not touch, move or allow drinks and such in therapy because it will distract the patient from the process of feeling. The emotions get so hard to work with, that a lot of folks will welcome any interruption to turn them off so they don't have to feel them. If you start to feel uncomfortable with processing the pain and see your water bottle sitting in front of you, a part of you will think that "hey, I really could use a drink of water right now" and then your thoughts are broken, and therefore, the process is either slowed or stopped.

If my T were to try and touch me in therapy, I would jump out of my skin and head for the door. Nothing against her, but with past trauma I'm very, very uncomfortable with people touching me. Period. That's just me.