Oddly enough older adult's would have young teens at this stage or family members of that age group so would be a handy thing for them to know lot's of people here share there netflix or YouTube premium etc with them to save a few pounds here and there.
You can uninstall afterwards. Also considering most of the hukd community are mainly older adults this deal wouldn't do very good since discord is aimed towards teens.
Its not just existing subscribers that are ineligible, its anyone thats ever had it before. Also if you are an xbox game pass member you can claim the same deal in the perks section of the app.