@mariusor I don't remember having such discussion. The SHOULD keyword is defined in RFC-2119:
This word, or the adjective "RECOMMENDED", mean that there may exist valid reasons in particular circumstances to ignore a particular item, but the full implications must be understood and carefully weighed before choosing a different course.
There are many valid reasons to not include @context. We also have almost 10 years of implementation experience and by now full implications are very well understood: by ignoring this recommendation we make messages smaller and developer experience better. No downside at all.