code style: why all require libraries must be localized ?

[bigfish02]

In apisix CODE_STYLE:

local ngx = ngx
local require = require

why ngx and require also need be localized?
In my opinion, it is redundant.

[tzssangglass]

read more: https://doc.yonyoucloud.com/doc/wiki/project/openresty-best-practice/local.html