It seems odd to me how in popular culture funerals have become an occasion to speak to the dead person. I'm aware that the popular mood (and quite possibly the default human position) is in many places pantheism, but I wonder how much of it is down to not learning Latin properly...
I'll explain. The traditional prayer for the departed goes something like this:
May he rest in peace and rise in glory.
In Latin, the first half is requiescat in pacem, which is famously shortened to R.I.P. It isn't talking to the deceased person; it's actually a prayer to God, or conceivably if used by non-Christians, a declaration of what you hope will happen. Technically, it's a third person singular present subjunctive, meaning "may he/she/it rest in peace".
However, the practice of praying for the dead was suppressed at the Reformation, because of the abuse of the (false) doctrine of Purgatory. far as I can tell, it was a good idea to get rid of the doctrine of Purgatory, but a bad idea to suppress praying for the dead completely.
Anyway, my point is that the main way the prayer was then remembered by the general populace was via the inscription R.I.P., which then got translated as "Rest in Peace", which is a second person imperative, looking like it is talking to the dead rather than the Latin which means "May (s)he rest in peace". And so (this is the speculative bit) it seems possible that the traditional practice of praying to God for the dead turned into talking to the dead, in part because we can't speak Latin properly and in part because of the Reformation overreaction against Catholic excesses.
Yes, I'm being speculative as to the causation, and I can also understand why people would want to say goodbye to their loved ones. It does, however, seem ironic if this idea is true, that in rejecting the Catholic idea that it is possible to pray for the dead and ask the dead to pray for them, the Protestants ended up talking to the dead which the Catholics didn't.