The Like Is Doing Distribution Work Here
A Threads post does not start with a guaranteed audience. Even accounts with large follower counts are competing for placement in For You, which is where the overwhelming majority of reading happens. The post is shown to a small sample, and what that sample does decides whether it goes further.
That is why likes matter disproportionately on Threads compared with X or Instagram. On X a post is pushed to your followers first and the like count mostly arrives afterwards as a verdict. On Threads the like arrives earlier in the sequence, as part of the evidence that decides whether there will be an audience at all.
It also means the honest description of what you are buying is different. Elsewhere, bought likes are social proof. Here they are social proof plus a nudge at the qualification stage — still no guarantee of reach, but acting on the mechanism rather than beside it.