The danger in giving crocodiles an old-fashioned is that to do it, you must first reach up inside them (their dick is in a pouch) to gain dong access. Some crocodiles don't mind, but others hate the intrusion. So to aid in the process, zookeepers sometimes build these little structures to help expose the genitals and aid the collection process. That's right: Crocodiles have personal dick-ramps.
As for the cranes, well, look up videos of any long-legged birds trying to mate with each other. The male has to leap onto the female's back in order to press their ... bird vents together. It's a messy process, essentially trying to scissor on stilts. Cranes at zoos are mostly kept in big open-air exhibits. To keep them in there, we have to stop them from flying. There are two ways to do this: wing clipping done every month or so, or pinioning, which permanently removes a section of the wing when the bird is very, very young. Both methods mess up the bird's balance and make it unable to align those "sex vents" (dibs on the German post-industrial band name) properly.
There's a whole bright galaxy of other reasons that artificial sperm collection makes more sense than natural sex in the zoological world: it can be dangerous to the animal's health; some critters are just bad at mating (do they make tiny fedoras for cranes?); and shipping a whole animal is much riskier than just giving that gorilla a lover's handshake and FedEx-ing the aftermath.
"That was great. Anyway, I got a lot of tourists to flash my butthole at tomorrow, so ... I'll call you."