It doesn't. Sampling is technically illegal. However the bootleg market is often too small to go noticed and larger artists get authorisation before sampling (or at the very least - releasing).
You do often see some artists turn a blind eye to sampling though. Particularly dance artists because many of them know their entire genre exists of the back of sampling. So it would be counterproductive / hypocritical for them to chase after royalties
You do often see some artists turn a blind eye to sampling though. Particularly dance artists because many of them know their entire genre exists of the back of sampling. So it would be counterproductive / hypocritical for them to chase after royalties