We have to stress it is a share, because no-one will get 100% click though rate, at the same time it is not a good strategy to optimize for a search term that has no traffic, or assume everyone knows your brand.
Adele Jolliffe wrote an interesting article about search share and has your moment arrived. She starts off by comparing the 1994 visit to Las Vegas, by the “Friends” TV series cast, being told their lives will never be the same again and that the “Share of Search” as now one of the the most important metrics within digital marketing. It could be compared to the “Share of Voice”, with say general elections, “who is getting heard the most”?
Immediate thoughts are, that those with a bigger brand will typically get a larger share, due to brand searches and clicks on a result with a trusted name. This metric can help a business understand where it stands with the competition, “who does the customer choose to click on”? This brand awareness can be powerful, outside of digital marketing but also with traditional types also.