You need the subscription ($5/mo) to publish your game to users who are <16.
16+ audiences have no requirement.
Kids doing their first obby are <16 and their friends are <16. It is not like roblox was cool for teenagers.
It is also that your game goes away when you stop paying. Which means, pay forever or you cant show it off anymore.
Which is the majority of the users[1], even more if you count that any user without age-check won't be able to access your game either.
[1]:https://www.statista.com/statistics/1190869/roblox-games-use...