They matter because AI with search does not only cite brands’ own websites: it also cites media, directories, comparisons and communities. If your competitor is in those sources and you are not, it starts ahead.
They are earned the slow, legitimate way: correct listings in directories and comparison sites, data or expertise offered to industry media, taking part in communities under your own name, and commercial collaborations labelled as such.
What not to do: buy reviews, votes or mentions and present them as spontaneous. In Spain covert advertising is an unfair commercial practice, and an AI may end up repeating exactly the fake review.