Oh boy, I'm sure you'll get a few responses to this thread.
Much the same as in cooking or baking, there are the ingredients and the process. In our case, the ingredients include everything we get from somewhere and someone else to craft a particular cheese style. The process...that's all in the talent, skill, imagination, diligence, and care of the cheesemaker. That process begins with the selection of milk, cultures, rennet, salt, etc. Making a poor choice in any of these before the cheesemaking is actually begun can bring poor results.
The attention to detail in making the cheese is crucial to crafting a cheese that delights the senses. If the cheesemaker isn't devoted to the task at hand or is distracted by outside influences, the temperature could climb out of control, the cultures could over-acidify, the family pet could enhance the effort with some "contribution", not checking/turning/washing a cheese on schedule could permit an out-of-control infection, or any number of other factors that reduce the possibility of an exceptional cheese product.
There are many other considerations for why the cheesemaker makes the cheese and not the provider of the milk, cultures, etc. IMHO, it's all in the hands of the cheese artisan.
In answer to your perceived need to acquire all of the cultures known to Man, you can stock a few cultures which will permit you to craft a wide variety of cheese styles: TA61, MM100, Flora Danica or Aroma B, PR, PLA or ARN, etc. Search on minimal culture collections or similar. It has been discussed previously.