Does a Druid in Wild Shape need hands to grapple?

The rules for grappling say “using at least one free hand”, but there are plenty of examples of creatures that grapple without hands–Giant Toad and Octopus, Giant Constrictor Snake, etc., and many of those do it automatically on a successful hit. So what about other creature types? A bear? A giant viper? A shark? Or is this a matter of DM judgment call?