While the predreadnoughts were definitely obsolescent, they were scrapped under the terms of the first post WWI naval treaty.
After WWII, only the USS Missouri was retained in active service, mostly because she was Trumans favorite ship but also because the RN an FN were keeping their last battleships in service for ceremonial and sentimental reasons (HMS Vanguard was heavily modified to operate as a royal yacht).
In fact, when the Missouri was decommissioned after Korea and relegated to the relative backwater of Puget Sound, Truman took it as a personal affront by Eisenhower himself.
The Naval Limitations Treaty — terms of which were basically drawn up between the United States and United Kingdom — “forced” the United States to do what we planned to do anyway. Several pre-dreadnoughts had been scrapped before the treaty was even negotiated, and the Navy planned to scrap the rest. A few were kept as monuments (notably Oregon), or auxiliaries (notably Kearsarge, converted to a crane ship), and a few demilitarized and kept as barracks ship (Illinois). Some had even been disposed of prior to WWI (Idaho and Mississippi — sold to Greece — among them).
But the Navy wanted them gone, regardless of the treaty. Similarly, all of the dreadnought battleships built prior to WWI were discarded immediately after WWII, with only the 2nd-generation dreadnoughts launched after WWI retained.