Problems with the "God explanation"
In all such cases, where there are no strong cultural beliefs regarding natural phenomena, scientific explanations are accepted and deeply ingrained. Its the reason, the instinctive response to "Why does apple fall down?" is "gravity", even amongst the most religious people. It's the reason God explanation for apples falling down seems ridiculous.
Similarly, the places where God explanation is emphasized the most are areas where the scientific explanations challenge the deeply held cultural and religious beliefs like evolution etc, of which some are cases where there is a scientific explanation but resisted, and some are cases where there isn't a scientific explanation yet and hence God is imputed.
In cases, where there is a scientific explanation but is still being resisted, it has simply to do with our difficulty to shed our deeply held cultural and religious beliefs. In other cases, where there isn't a scientific explanation yet, God explanation isn't still a valid explanation. Read on for why it's the case.
2. "God explanation" is non-falsifiable: It means that you can't actually test for it. You could replace "God" with anything in that explanation and make the same argument. Consider an alternate explanation - "A microbe in a distant galaxy is making apples fall, charges and magnets interact". The "Microbe as the explanation" is no different from the "God" as an explanation. How are you going to determine which one is correct? You can't.
The same goes for the "falsifiable statements but practically impossible to falsify" statements. Bertrand Russel has a term for it, popularly called "Russel's teapot": It's an argument where one says that there's a teapot revolving in our solar system. Since it's nearly impossible to falsify it, they would reason "because you are not able to NOT prove me wrong, I am right". This would eventually mean that one should accept that there is a teapot revolving in our solar system.
The beauty of non-falsifiable hypotheses is that one can justify anything using them because they are either non-falsifiable or too difficult to falsify. Hence, they are NOT accepted as reasons.
For instance, the scientific explanation of gravity merely does not say that Earth attracts the apple. It gives a formula for calculating the speed of motion, the direction of force and so on. It also accounts for all the observed data.
"God explanation" as an explanation for "apple falling down", on the other hand, does NOT do any of this. It gives no additional information on the motion of the apple. God explanation is thus said to have zero explanatory power.
5. God explanation does NOT have a good history of being correct: People invoked "God explanation" in the past for many things - God creates cyclones, God creates floods, God created humans etc. As science progressed, we understood these phenomena and scientific explanations replaced 'God explanation'. What was once thought to be the realm of God is the ream of science today. One should hence note this point while invoking God explanation. What some may now attribute to God may become Science in the future.
In short, a "God explanation" is no explanation.
Apart from the cognitive reasons, there are logical loopholes with the "God explanation".
Characteristics of an acceptable explanation for natural phenomena
God explanation makes no prediction.
The process is straightforward for physical laws. You just show an experiment or a case, where objects don't follow Newton's laws, you have successfully challenged the Newtonian theory, for the objects of that scale. In other cases like evolution, if we say that evolution is the scientific explanation of species, we should also be able to list out the nature of the evidence which could disprove evolution.
God explanation gives no such criteria to disprove because it's not a falsifiable explanation.
Applying the metrics of an acceptable explanation to "God as an explanation for the origin of humans"
Within the evolutionary paradigm itself, there are other alternatives proposed for the mechanism of evolution like Lamarckism etc., but the Darwinian explanation has the greatest explanatory power.
God explanation for the "Origin of Life"
The Big Bang: The "God explanation" is no explanation
In cases where there isn't yet scientific progress, God explanation is still no explanation. Science may not know many things but the way to know it is through the scientific method. Imputing non-falsifiable theories like God has many loopholes like - we can impute anything in that place (microorganism in the distant planet) and make the same claim, and there is no way to know which one is true. It further doesn't have explanatory power. Settling for God explanation curtails the human progress. Here again, God explanation doesn't stand up to scrutiny and hence God explanation is no explanation.
So, next time, whenever you come across a natural phenomenon that you don't understand yet, think twice before invoking "God explanation"! "God explanation" is "no explanation".