CHI is a huge conference. More than 1000 papers were submitted last year. A designated committee chooses 1% of the submitted papers to receive the best papers awards which explains the number of awarded papers.
Having 2 or 3 best paper awards I can understand, but having a dozen is cheating. Many of the other top conferences like WWW, AAAI, and SIGIR have nearly 1,000 submissions also and they only have a single best paper award.