I'm certain the most common prayer is "Please give me (something)." Singer Janis Joplin had it right in her parody of Christianity lyrics, "Lord won't you buy me a Mercedes Benz. My friends all drive Porches I must make amends."
Prayers to an invisible god and letters to an invisible Santa Claus seem identical to me. Both are about self.
This past week I visited the State Capital building close to where I now live in Iowa. I went there to watch an atheist deliver a humanist invocation to begin the daily work or the Iowa Senate. She read a statement of hope that all lawmakers will make every citizen feel he/she is part of the state's political and governmental affairs. She did a nice job.
There was some concern before hand about the reaction of Senators. That is because a few years ago a Wiccan led an Invocation. Several Senators stood up and turned their backs. Outside the chambers some religious people held a rally expressing their condemnation of Wiccans. There was no hostile reaction to the atheism Invocation. Afterwards, some of us went out for lunch and we all hoped a Wiccan could again present an Invocation and we could see if attitudes have changed.
I don't see harm to others of prayers that treat God as Santa Claus. Nor is there harm from other religions which do not harm people such as that practiced by Wiccans.
Also, there would be no harm to eliminating the custom of an Invocation.