Probably the Auto owner or driver is having a faith in the God and he wanted to show that by writing on the back of the auto. The existence of God is a belief and it your choice. We should remember hin all 24X7. Not only when we are in difficulties but also when we are satisfied also. That is why elders say before you start eating you should thank God for the food on that day and then start eating.
In this society, we have atheists as well as religious persons who blindly follow his path. The belief in God is beyond the above aspects and can be in the evergreen argument of its presence.
If we believe in God, we would accept that he is omnipresent,he is literally in our daily lives with us. We should not just blindly put everything in the name of God and sit back at home, nothing will happen. We need to put in our effort and hard work in whatever good we do, then it's up to Him to guide us in our venture to succeed or another learning experience.
The second part is more realistic to us if you think at a higher level, nothing is more important than the good things we associate with God, purity, honesty, helping others, being healthy. Riches, power, luxuries of life come after all the above.
I agree with you, many of us think about God in difficult times and forget Him during good times.