Max Trinidad notes that SSMS 17.4 gets rid of the SQLPS module:
After SSMS Version 17.4 was release back in December, SQLPS module is no longer available. So, if you try to use the “Start PowerShell” from any of the database object, you’ll get the message “No SQL Server cmdlets found…” popup message.
And good riddance. Even in 2008, the SQLPS method of dealing with Powershell was obsolete, as Powershell modules were supposed to be snap-ins rather than independent shells. The SQL Server Powershell module is a major improvement in that regard.