Heya fandomstranger! They will and ARE on DCU/I! Of course, we are still going through the process of digitizing all the golden age comics. I just finished creating a summary of all the questions our DC Archivist answered in a Q&A in May. He will be back next Wednesday to answer more questions, so if you have titles you’d like to see, I think he would help to shed some light on why some haven’t appeared and when to expect others.
His answers are really fascinating, and I highly encourage you to justify the work I did on the summary by checking out the answers here. Feel free to drop a question just like this in the comments on that topic, as well!