I cant really answer the question itself, but I will share my brief contemplation.
“How belief in rebirth is conducive to dharma practice?”
1. Avoiding annihilationism and materialism
What is the first natural thought that arise if people believe that this life is the only one, there is no life before this, and there is no life after death?
To live a good life.
But what is a good life? Well people will get married and have family. They will work to get money. And then when they have money, they will buy things to satisfy their desire.
Some people will even do crime to get money. “It is alright as long as I don’t get caught”.
And then because desire is endless, they will repeat this cycle again and again. And because samsara is by nature unsatisfactory and satisfaction by nature is diminishing, people will seek greater pleasure, and so they will work harder to satisfy their ever increasing desire. Until finally they become old and run out of energy and then question their life “What did I do? What is the meaning of all of this”
When I briefly describe this phenomena in original thread. Another person said that doing something again and again expecting something different is insanity, and so he reject my argument, assuming that people can realize the truth. But we can see the world right now, the world is insane and billions of people are doing exactly this. Even buddhists are still doing this at some level.
Believing in rebirth helps us in not getting attached to this current life. This body, the wealth and money, the family and relatives and friends, our current entertainment and hobbies. These will all gone, at death we will be reborn and acquire new ones. This is the early steps in dealing with attachment.
2. Preventing suicide
The above scenario is for people that have everything go well in life. What about people who don’t?
If someone is so cornered by suffering and think that death will end everything, he might choose suicide.
Also, some people may realize that sensual desire is unsatisfactory. These people, lacking information about jhana pleasure, or information about escaping samsara, what will they do? They feel that life is empty, meaningless, bland, boring, hopeless. They might do suicide. I think there is real life example of this.
3. Preventing hatred to universe
I am sure that I am not the only one who sometimes think that the world is unfair. Why is that person can become filthy rich, but I am not. Why is that one born in rich and high family, but I am not? Why that person is famous, talented, beautiful, charismatic etc, but I am not?
And there are people that become atheist because religions answer with “God’s will, God’s secret, God’s plan, don’t question it.”
If there is no rebirth and kamma, it means that everything that happen to us is due to massive game of chance/ coincidence. There is no reason why I am born in rich family, I just happen to be born there. Lucky me. There is no reason I am so ugly. It is just happen, unlucky me. There is no reason or cause for this happening.
This train of thought will lead to thinking that the world is unfair. There will be hatred to everything. Hatred is hindrance. People comparing their life with others, and think that they are miserable, they have unhappy life. Some will even think that this life is hopeless, lets suicide.
Instead, the right view and right thinking about rebirth and kamma can prevent this. Thinking that this is the life I have, because of my past deeds. I deserve this, It cant be changed, now lets work with what I have for future rebirth and liberation.
(Not saying that rebirth and kamma cannot result in wrong view, or fatalism, or any other wrong things)
This is not stream entry level, this is waaay below it at beginner level.
There is desire and hatred at very coarse level. Desire and hatred is hindrance, right?
So at this level, belief about rebirth is conducive to dharma.