SharePoint 2013 - SHARE - Only a limited set of people are allowed to share this content

In SharePoint 2013 on-premises, there is a confusing user experience with
the ability to “share” documents for visitors and members unless you have set up
outgoing e-mail on your farm and enabled access requests for your site. While the
Share option is not available in the document ribbon
for visitors and members, it
is visible from the list item dialog as shown in Figure 12-13. Clicking the Share
option in this scenario without access requests and e-mail enabled returns an error
message: “Sorry, something went wrong. Only a limited set of people are allowed
to share this content.” This is actually by design, though the error message is a
little confusing. Nothing really went wrong; the user just doesn’t have permission
to share a document if the site doesn’t have “Allow access requests” turned on.
This capability is enabled in Site Settings > Site permissions, and when enabled,
it allows visitors and members to initiate an internal document-sharing request that
goes to the site owner. In SharePoint Online, visitors and members can initiate a
sharing request for a document in both the ribbon and in the item dialog, but all of
the requests go to the site owner for approval.