They are slow because that helps conserve energy. They spend around 18 hours a day sleeping upside down in trees.
A question to evolutionists could be that in the supposed 60 million years since they have supposedly evolved, why hasn’t another predator “super”-evolved to wipe them out. They are camouflaged, but is that enough for surviving 60 million years while other things are supposedly evolving?
See more here: http://www.creationmoments.com/radio/transcripts/real-sloth