...or is it because it's simply too inconvenient to build a culture that cherishes life, every life.

"Inconvenient" isn't the right word. When we start defining what such a culture would look like we get contradictions and outcomes the vast majority of people would never tollerate.

We aren't willing to give the State the ability to order people to give up their internal organs for other people's use... or to let the State permanently damage the health of people so that others can prosper. We aren't willing to execute or imprison the large numbers of women who would get abortions anyway even if it were illegal.

So both the theory and the outcome look pretty ugly when we assume the State can't magically make people believe what we'd like them to.