"Who changes the name?"
Usually scientists, biologists, or other scientist type people will find suprising trait or DNA sequence that is different enough within a genus or within multiple genuses that either splits them or combines them. I'm not sure what caused the scabiosa-type plants to get split. Not too sure about this.
"will my scabiosa seed packets be collector's items now?"
Well, hmmm maybe? Scabiosa is still Scabiosa. If the Scabiosa is a different genus now, well now it's a different genus. If it's still Scabiosa, it's still as common or as rare as before
"Seriously though, how or why does the name of a flower change? "
For more sorting. For example, if we had cherries, apricots, plums and peaches in a lump, it might be harder to sort, whereas having them seperate because of their differences in fruit shape or growth would be easier. In other cases it's that some species in a genus might have very different DNA sequences, so much that they seperate it into a new genus. Sometimes genus are combined, because they are genetically very similar, similar enough to be so closely related to be in the same genus.
