Why shouldn't voters get a say in these matters? If it is so important that experts make the calls, then convince the voters to vote for allowing the experts to make the calls. If the voters don't trust the experts to such an extent they rather risk screwing everything up, then that is what we will have to live with.

For a interesting thought, what about matters of brain development and ability to reason? Why should voters get to decide on matters such as when we are considered adults or when consenting to contracts or sex is possible. For nuclear or medical expertise, there is at least expertise. For matters of brain development, the science is still very young and limited. Or even on a greater extent, why should a voter be given power in matters that require ethical expertise? Matters that require legal expertise?