I created identical formula fields on the Lead and Contact. But when I try to map them together the Contact version of the field is not available in the picklist. This is my first time creating a formula field. Is it not possible to map Lead and Contact formula fields together?

I would like to create an "Account Score" field that sums the values of the Score field values on the Contacts attached to the Account. I found an old thread from 2012 that seems to say this is impossible. It seems like such an obvious thing to want to do  - especially with all the focus on Account Based Marketing these days - so I was surprised. It's now 5 years since the old post I found. Has anything changed?

I created identical formula fields on the Lead and Contact. But when I try to map them together the Contact version of the field is not available in the picklist. This is my first time creating a formula field. Is it not possible to map Lead and Contact formula fields together?