relic shield on adc?

Watching some international streams, i been seeing a few carries get relic shield as one of the first 3 items they purchase. Spoils of war granting 15 hp on minion kill, also increase gold share with support. It appears they do very well when using it, however i do not fully understand why they choose it (apart from lane gold share and the hp restore). Anyone care to give some input?
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