Vendors don’t even agree on whether the :gun: is a revolver or an automatic or space ray guns or even water guns, btw it’s an 1911 in original DoCoMo emojis
Same reason why Gmail uses their own emojis rather than the system ones — (as said above) branding. When you send a tweet, Twitter wants it to look identical across all devices. The classic native UI vs cross-platform UI debate in a nutshell.
