I hadn't considered that. For a moment I thought maybe they were actually doing something for the community by stopping award spammers from inflating their own comments. But no, it's just because they think they can squeeze $2 more out of a user if no one has the option to thrust premium on them and they actually have to buy it themselves.
Except that makes no sense in practical terms because not enough people care about premium to offset the fact that a person can purchase gold awards as many times as they can afford.
Reddit corporate sure does like shooting itself in the foot