You can't launch SDBs sitting at home.
Those SDBs require launch platforms to fly inside or near enemy airspace.
Each launch platform costs money, and needs support assets, which also cost money.
With that said, SDBs are useful, but they're not a first-wave weapon.
Yes, I don't expect SDBs to be a first wave weapon.
But I would expect them to form part of a second wave attack (at least in the 1st Island Chain) starting some 3 hours after the first wave.
The rationale for this is that the it takes a minimum of 3-4 hours to repair a runway and most fighter jets only have a maximum endurance of 2-3 hours. So any opposing fighter jets are either trapped on the ground or have run out of fuel in the sky.