>go to smogon dex
>look at bro's move sets
Crobat @ Choice Band
EVs: 252 Atk / 4 SpD / 252 Spe
- Brave Bird
- Cross Poison/defog
- Defog/sleep talk
>defog with choice band
>sleep talk with no rest.
Not defending Smogon here but actual good players and reasonable sets.
Sleep Talk on Band and Scarf Pokemon has been a thing since Gen 4 and acceptable in Gen 3 wih Band.
Got very common in Gen 5 OU and UU (Terrakion in Ubers) because of Breloom, Venusuar, Roserade and Amoongus: Tornadus, Dragons, Terrakion, Darmanitan, Crobat, Staraptor, Heracross and many other HO choiced mons used to successfully run it their sets. Those sets and Pokemon basically offer you a sleep fodder that isn't actually a dead weight and can even put in some kills.
Same thing in Gen 6 except less Pokemon used due to the Spore nerf and the pressure put on its users. Talonflame is definitely the last addition to the choiced Sleep Talk team. While Crobat does well in UU with Doublade being Hypnosis / Grasswhistle bait sometimes and for other more common sleeping moves.
It's just basic teambuilding and common sense.
Sleep was nerfed in G6. The most common sleep-inducing move is Spore.
Ergo, Sleep Powder, Hypnosis, Spore, Yawn, and Relic Song are all, to certain extent, nerfed as of Gen 6's mechanics.
If OP would've had enough attention to read the set description, he would have found this:
>Finally, the last moveslot is a toss-up between Defog, which can clear entry hazards for Crobat's team in a pinch, and Sleep Talk, which allows Crobat to absorb sleep-inducing moves.