I've never understood why people equate asking a person face to face or on the phone as the same as asking someone in Heaven.
If I have a conversation with someone, I know they can hear me. "Hey Bob. Would you pray for me?" Bob says "Sure".
It's not possible to have a conversation with someone who can't hear me. "Hey Bob. You're in another state and you can't hear me, but would you pray for me?" Silence, because I'm in Iowa and Bob is in New York and I didn't use the phone.
Asking someone in heaven to pray for me is more like the second example rather than the first. If you have no promise (or reasonable expectation) that someone will hear you, how can you expect your request to be anything other than wasted breath?
But, they can hear you. See my post #65.
Because they want to justify their doctrine and practice and it's the only way they can do it.