DL is far from unique in this. Both AA & UA sell tight connections at lower fares. This is largely because such connections are often not desireable. On the other hand, if you misconnect, DL will rebook you onto the next flight with availability. As you have not provided the exact date, routing, and flight numbers, nobody here can advise you as to what might be available.
Bottom line here is that if you book the connection, you should plan on flying it. SDC might be available and will likely cost $75. Only you can evaluate the value of $75 up front in order to make it your destination vs. the hassle and cost of a misconnect, e.g. missed meeting or whatever the purpose is of your trip.