Before March 29, a Skype Manager administrator can take back allocated Skype numbers and credits from a managed account. After that date, administrators will still be able to assign Skype Credit amounts, subscriptions and Skype Numbers to personal accounts, but they won't be able to reset passwords ore delete these accounts.
Customers who want individual Skype accounts to be managed centrally by an administrator should move to Skype for Business to continue to manage accounts this way, according to Microsoft's blog post.
As to why Microsoft is making this change, the official reason stated in today's blog post is to give Skype users more flexibility. But wanting to move more users to Skype for Business is likely the actual reason. (I asked Microsoft officials for more on the reasoning behind the move, but haven't heard back.)