Why? Because this release (from the 2012–2013 era) was the last "lightweight" version before the heavy integration of Oracle REST Data Services (ORDS) and Java 8 requirements.
Rediscovering the Past: A Guide to Downloading Oracle SQL Developer 3.2.20.10 Oracle Sql Developer 3.2.20.10 Download
Once you download it, zip it up and save it to your company's internal drive. Oracle delists old versions occasionally, and you don't want to be searching for a 32-bit JDK 6 installer at 5 PM on a Friday. Have a legacy war story about SQL Developer 3.2? Let me know in the comments below. Oracle Sql Developer 3.2.20.10 Download