Is the sign-up requirement what actually kills shared lists?

Disclosure first: I build a shared-list app, so I am not neutral. But I keep running into something I would like other people's read on. Every shared-list tool I know asks everyone in the group to install it and create an account before the list works. In my experience that is where sharing dies — not because the apps are bad, but because the person you are sharing with has to do three things before they can tick off "milk". Most people give up and paste the list into a chat message instead.

So my question to people who have built collaborative tools: have you found the same, and what did you do about it? Did you make accounts optional, defer them until someone needed sync across devices, or did you decide the account was worth the drop-off because of what it enables later?

I am especially interested in cases where you removed a sign-up and it did not help — that would be more useful to me than agreement.