Originally Posted by bgriff

Ah, I see what you mean. They are blocking the regular seats in an effort to get you to pay for the premium seats. So there is a little bit of a conspiracy

And the answer here is similar that yes, Delta does block some regular seats (2 rows at the back of every plane). I assume those seats open up at T-24 but frankly I've never really paid attention since, unlike the C+ seats at the front, I have never been eagerly awaiting the chance to swap into seats at the back of the plane.

If you are a family traveling together you might be able to call Delta and get them to give you those seats at the back, though there is an excellent chance the agent may also be trained to try to upsell you to the preferred seats instead.

You can also refuse to pay for preferred seats and take your chances with what you are assigned at the gate at departure, but the seats might not be together.