While Frontpage does not allow promotions in clubs or stock feeds, a creator is free to post anything to your followers, including promotions.
A profile post lets you reach your followers in an UNMODERATED way. You may promote your offerings, other ideas which can’t be put in clubs right now, or anything else.
So that people don’t abuse profile posts from visibility beyond their followers, profile posts can’t have #stocktags.
PS: Users on Frontpage discover your posts in clubs or stock feeds. If they find posts valuable, they follow the creator to get more of their posts on their feed.