Why does support Shen feel so useful when standing around and doing nothing

I don't know why, but Shen's presence in lane is just so huge even if he does nothing but stand back with ancient coin. If Blitz pulls the ADC in, he can taunt and Q, then use his W when the ADC is trading.

He's not like Thresh, who hooks in kills, or even Soraka, who pokes with Q and actively heals and silences as needed. Instead, Shen just stands around waiting for the perfect engage before completely turning it around.

I played one game with him and got the lowest score out of everyone, but my ADC had so little deaths that she could just roam around and go where she pleases. Somehow, I still got an A- like the fed jungler (ahem, low support standards rito.)