I agree to a point, scientifically there should be no sentiment whatsoever. But he isn't making programmes purely about/for science. A large part of the remit is to interest, create sympathy and therefore educate the general public about our world. Animals that are 'close' to humans lend...
There is, it just disappeared over the horizon:
http://www.northstandchat.com/showthread.php?368032-Dynasties-narrated-by-David-Attenborough-starts-Sunday