This is a welcoming custom. It is such a good manga, and the live action movie is brilliant thanks to being true to it, making it the only Hollywood manga adaptation with positive reception from fans. (Every other manga adaptation sucks for many reasons)
Helps that the director and producer knew their stuff thanks to being big anime nerds. (Yes, that means James Cameron and Robert Rodriguez are weebs like us. XD) That's what made it stand out after every other failed manga adaptation bombed.
(There's no defending them. Especially Ghost in the Shell which had really racist implications at the end due to the whitewashing)

Please note that Gally is the name given to Alita in the original Japanese and in the OVA.