Currently, public sub counts are abbreviated in most but not all places across YouTube. In August, we’ll make this more consistent by always showing abbreviated sub counts publicly. Creators: You’ll still see your full sub count in Studio! Learn more → http://yt.be/help/abbrev-count …pic.twitter.com/pmaKk4EU4k
Youtubers won't know whether they are doing things right or wrong. People use the sub counter to see whether they are losing or gaining subs, and they act accordingly. You can't notify them only AFTER they've lost a 100k