Obviously because the league has not yet decided to make an example of them as they have done with Kaep and Reid. Similar to a situation where employees are trying to organize a union, the company doesn't usually fire everyone who attended a union organizing meeting, just the leaders, to make an example of them.
And Stills, Jenkins and Wilson are active players on NFL rosters, to suspend, fine, or punish them would be a violation of the current CBA, while there is no penalty for not hiring a free agent (absent proof of blackballing/collusion).