Civilizations started around river valleys since it is a good place for agriculture and it makes a good place for trade
Such places are:
- The Nile for Egypt
- The Tigris and Euphrates for Mesopotamia
- The Indus river for the Indus Valley Civilizations
- The Yellow River for China
However, these aren't the only river valleys that are advantageous to farming
Other places are:
- The Mississippi river
- The Parana river
- The Volga river
- The Rhine river
- The Ganges river
- The Irrawaddy river
- The Chao Phraya river
- The Mekong river
- The Yangtze river
Some of these areas are more fertile than the rivers on which these 4 cradles of civilization lie on.
The Ganges is more fertile than the Indus due to it collecting more residue due to its size. The same could be said for the Yangtze in replacement of the Yellow River for China.
The Mississippi and Parana rivers are perfect places for Mesoamerican civilizations to go farm on but instead they decided to say "fuck it, lets do it on the mountains instead"
So why don't these river areas house major civilizations despite being more advantageous?
Is it merely by chance that these regions got ignored for some other regions?
While it is not exactly your question, u/Reedstilt talked about the Mississippian culture in the somewhat related q: https://www.reddit.com/r/AskHistorians/comments/2rrm1y/why_are_there_no_ancient_native_american_cities/
At least in the case of the Mississippi, the answer is "it did".
Questions around why civilizations did or did not originate in various regions get asked fairly regularly (will share a list at the end of this post). Definitely not trying to discourage further answers, but might be helpful to read some of these past answers as some of them are quite interesting.
But if I had to summarize a few key takeaways, the big one is that there isn't going to be a simple answer to this question. As /u/jschooltiger writes here, it is always hard to answer the question of why didn't something happen in history, because we don't have a clear way to prove counterfactuals - there's no way for us to run an experiment, change a few variables, and see what would have needed to change for it to happen.
In particular, for this specific example, the question essentially pre-supposes that civilization will naturally emerge in sufficiently fertile river valleys, which is why we frame the question of why certain river valleys did not give rise to civilizations. As you yourself note, there are more examples of fertile river valleys that did not serve as the cradles of civilizations than there are examples of those that did, which suggests that agricultural fertility is a necessary but insufficient criteria for the emergence of civilization.
Moreover, the similarity between the cradles of civilization is often overstated. For instance, the Nile and Mesopotamian civilizations originated around the river deltas of floodplains, while the Yellow River and Indus River civilizations originated far inland in the midsection of the river. The Nile, Indus, as well as the origins of Mesoamerican and Peruvian civilization are all subtropical; Mesopotamia and the Yellow River are more temperate. All of this hints that the origin of civilization may not be a simple matter of geographical determinism, which in turn means that we cannot look solely at geographical factors when trying to understand the beginnings of city-building civilization.
Examples: https://www.reddit.com/r/AskHistorians/comments/ecu2fp/why_did_an_egyptianlike_civilization_never_rise/ https://www.reddit.com/r/AskHistorians/comments/1yr77a/why_did_no_civilization_develop_along_the_banks/ https://www.reddit.com/r/AskHistorians/comments/3e4m08/why_did_the_land_around_the_danube_not_give_rise/ https://www.reddit.com/r/AskHistorians/comments/99lsax/why_did_civilizations_thrive_in_persia_and_the/ https://www.reddit.com/r/AskHistorians/comments/31tech/all_the_great_ancient_civilizations_of_the_old/