Because we created the ecoTrain group and we created the tag, which is a name tag and not a topic tag.
Other groups like @familyprotection or individuals like @quinneaker are also using their own tags as well.
So I would think it is common sense and common courtesy to not use those tags if you are not a member of the group or the individual itself.
But I understand that people might sometimes think ecoTrain is a topic, but it is not, therefore the friendly request to not use the tag, and usually people understand our issue and refrain from using the tag next time.