Not as much as I used to, I used to attend ceremonies for PWPs all the time. Now I don't often because I usually forget sometimes what PWP I want built.
I've attend all but a few. Those where I picked no because I was in a hurry.
It's a good way to find out who is outside. I've have a lot of short villagers in one town and it's hard to find them.
Also for the ping for a new PWP.
Sometimes. Sometimes I attend them, because a friend told me that it increases the chances of a new publics works project being requested, but I think that's not true.
I attend them all because of the confetti! Plus on my cycling town, I was putting in PWP's to get a perfect town rating so I could stock up on jacob's ladders. I would often forgo the ceremony, but it made me feel guilty.