For 30 Rock and Parks and Rec, weren't those appearances after the people were already prominent and/or in office?
The 30 Rock/Al Gore example in particular happened years after he was done running for public office.
And even Parks and Rec wasn't so much advocating for Joe Biden/Michelle Obama as having a left leaning, political character be excited about the opportunity to meet them. I can also remember John McCain appearing on Parks and Rec.