Here it goes:
1) A handshake tells me a lot about a person I meet for the first time. I'm sure there have been books written about the different handshake styles; "limp", "overly aggressive", "short and brief", etc. For me, I like being around others who typically have a confident and warm handshake. It is strong without being overbearing. I can usually tell who I can get along with and who to avoid via one simple handshake.
2) It tells me who to avoid. On a few different occasions, I have met people whose handshake was...how to put this...icky. Red flag warnings go up and I immediately sense that this individual is "unhealthy" and to be avoided. I don't know if the person has done illegal or hurtful things to others, or if they are users and manipulaters, but something isn't right. The handshake doesn't change and it doesn't lie. I avoid icky people.
3) Shaking hands is oft grounding, for this autistic. It brings me out of my distant, inner bubble and actively engages me with the current situation.
4) Having PTSD, a handshake a: tells me if a person is good or bad and b: it desensitizes or tells my brain that this isn't a person who has previously hurt me. The primitive, survival part of my brain remembers and fears touch, because my abusers physically hurt me. A hand shake reaches that part of my brain and distinguishes between past abuser and present not my abuser.
5) I shake hands to say "hello".
6) To say "goodbye".
7) and to say "Thank You." Gestures are sometimes easier than words:)
8) A handshake tells me who I'm likely to get along with, who is an egotistic, who is to be avoided, who is kind and caring.
Shaking hands is just part of who I am. I like it. I have my reasons:)