I received a doctorate degree in literature from Hiroshima University for the conversion of merit to hungry ghosts. Please don't think it's “that stupid,” and read it for now.
A memorial service is taking care of someone by giving something to them.
It is a good act done to people who are originally alive, especially those who are superior.
However, if the person I want to make a memorial service for has passed away, I can't do anything directly for them, so I do something good myself and hand over that merit to the deceased. It's called merit conversion.
The person I want to make a memorial service for hasn't disappeared either; they have been reborn somewhere in reincarnation and are probably still doing their best, so surprisingly, the feeling of a memorial service from here on out arrived and they cheer me up.
That's why doing it for a memorial service is meaningless unless it's a good act.
The most popular “give sutra/have a monk give it to you” is a good act of giving an offering to a monk.
Monks can just receive the offering and go home, but in order for the client to do greater good deeds, they will do their best “so that the client's feelings are pure” by giving sutras. After the sutras, they recite Kaikōmon, and the merits of “ascetic practice,” which cleans the heart by listening to the sutras, are transferred to the deceased.
It's such a system, so it's good to give sutras, but if you ask a temple, you can rest assured that there is at least a good act of making an offering.
If you do it yourself, it's OK if you have a sense of closeness to the Buddha's path and recite sutras to clear your mind. I'm a little worried that “if I give you sutras, it will be a memorial service.”
For details, see my book “Why can merit be converted?” The booklet “What is a memorial service?” which can also be read on (Kokusho Publishing Association) and the Seikyo-ji Temple website where I work Please refer to etc.