PowerPivot is definitely available to Office 2013 and 2016 users. However, Microsoft has limited its availability to certain versions of Office. Only Office Professional Plus, Office 365 Pro Plus, and Office 365 Enterprise editions have Inquire, PowerPivot and Power View.

If PowerPivot is not a selectable option, this means you’re using either the Home, Student or Standard version of Office which doesn’t have the ability to add the COM Add in.

https://support.office.com/en-us/article/Start-the-Power-Pivot-in-Microsoft-Excel-add-in-a891a66d-36e3-43fc-81e8-fc4798f39ea8?ui=en-US&rs=en-US&ad=US