One can believe in God and also accept the science of chemistry. They are not at all incompatible. Given that the building-blocks of proteins appear in nature, it certainly isn't inconceivable that with sufficient time, and with oceans filled with pre-organic molecules floating around, a self-replicator could eventually get formed. One is enough. After that the fun starts. None of this rules out God, so I wonder why so many religious folk simply won't accept that life could have begun as a natural process.
That is due to the fact that you are omitting something. The process may be natural, but it is so unlikely as to be "impossible". Chemicals form compounds in repeatable and predictable ways. Life changes the chemistry, by having catalysts available and proximal to the reactants. Without those conditions the compounds necessary for life are not formed. Competing reactions will destroy complex chemicals before they have the opportunity to be of any utility in the formation of life. In a nutshell, if the compounds are stable in the environment producing them they will use up the reactants in their formation and be extremely difficult to catabolize. If they are unstable in the same environment, they will be catabolized before they are complex enough to do anything. This observation is valid for dimers through the longest stable polymer. There are countless competing reactions contending in a wild lifeless "soup". The "astronomical" numbers presented for the improbability of the formation of the putative chemical antecedents of life only consider one type of reaction in the calculations.
The first reason is that attempts are made to rule out God using the authority of science -- think of Singer and Sagan. I think the debate would be far less contentious if biologists were to say God caused life to somehow start and this is how we think He did it because etc. This sort of qualification was once rather common.
The second reason is that science considers the generation of life from non-life to be impossible. So when someone declares as a certainty that this happened via a natural process, others reasonably become suspicious and behave accordingly.
The science in this case is actually biology - no natural DNA not made by living things has ever been found or produced in any natural way in a laboratory. In addition, there is no chemical basis for the sequences in DNA and one would need at least a string of half a million DNA bases for the first reproductive life on earth. So, it is quite impossible according to the scientific facts and no one has been able to even formulate a theory of abiogenesis which fits the present scientific facts. Science is not about possibilities. Events which have 1 chance in an infinite amount of chances of happening are not science and that is what we are speaking about with abiogenesis. Only someone devoutly atheistic which totally disregards the scientific evidence would say that life can come from non-living matter.