I think you've confused basic economy and regular economy. In Basic Economy you can't choose any seat. In regular economy you can only choose from seats that are not blocked (or pay an upcharge). If anything, the blocked seats would encourage you to purchase basic economy, since you can't get a good seat even if you purchase regular economy.

But it's not a conspiracy. Those seats can be selected for free by elite status holders. So that status holders who buy tickets closer to departure will not be stuck in a middle seat.