On https://netbsd.org/docs/guide/en/chap-boot.html#chap-boot-pkgsrc
Storing third-party software On many UNIX-like systems the directory structure under /usr/local is reserved for applications and files which are independent of the system's software management. This convention is the reason why most software developers expect their software to be installed under /usr/local. NetBSD has no /usr/local directory, but it can be created manually if needed. NetBSD does not care about anything installed under /usr/local, so this task is left to you as the system administrator.
This is a point for NetBSD, at my first thought. /usr/local sucks. (You can safely skip two line below.) Why separating "distro"-installed packages with user-installed packages? They are just packages that are not necessary for the system to boot up. Skipped over the pain installing NetBSD, I found that there is no /usr/local, but /usr/pkg with the identical directory structure !!! Will it worth mentioning?
