Lack of SkyMiles low level awards is unquestionably the most discussed topic on the Delta forum. Search, and you will find complaints galore.
Just to summarize, Delta Airlines is in business to SELL tickets to consumers. Similarly, SkyMiles exists in order to SELL miles to partners like American Express. SkyMiles has the further mission of bait-and-switch, i.e. advertising free travel awards at low mileage redemptions.
Delta Airlines works very hard to promulgate the myth of free domestic travel at 25,000 miles and free international business class travel at 100,000 miles. These free travel options are meant to appear on the awards chart only and to make SkyMiles appear competitive with other FF programs. Except for the rare exception, they are not actually available. By design, Delta makes sure they do not pop up on the award calendar. The SkyMiles award calendar offers domestic free coach travel at 80,000 miles and international business class free travel at 360,000 miles. These are the realistic redemption levels --not those shown on the SkyMiles award chart.
SkyMiles members delude themselves into thinking that mileage redemption is possible at any of the low levels shown on the SkyMiles award chart.