Probably because its not their natural environment. But in captivity they get lazy and often hardly use their (often limited) climbing facilities. More true of Bornean Orangs generally.
No. He was born in Europe and transferred to Dublin as an adult. He was handraised and has also never been any use as a breeding animal. I think that was one reason Dublin were happy to move him on to Dudley and why Dudley had to then later bring in the younger male 'Jorong' in order to breed them again.