Why don't the trams go to T-Centralen?
The name “Djurgårdslinjen” is used for the heritage service operated between Norrmalmstorg and Djurgården (line 7N) since 1991. Since 2010, SL operates regular tram service on the line; this is known as Spårväg City, line 7.
Several of Djurgårdslinjen's trams are single-ended, requiring a loop to reverse. Unfortunately, T-Centralen is a stub terminal with no loop, so single-ended trams cannot run there.
Occasional extra runs on Djurgårdslinjen go to T-Centralen, but the regular service always originates from Norrmalmstorg.