Great question — answering as the UphillTech team:
First, let's make 2 assumptions: Hyperspace collisions have happened in the past. In general, people know the consequences, and they know it's very messy. ("Ain't like dusting crops, boy!") The rebel military leaders aren't stupid. Admiral Akbar, General Organa, and Vice-Admiral Hondo fully understand what a "Hyperspace Kamikaze" attack would accomplish, and they've simply chosen not to do it until now. Now, speculation on why we haven't seen it before: 1. Relative ship size matters. If an X-Wing tried to hyperspace through the Death Star, nothing would happen except the X-Wing blowing up. 2. The smaller ship gets disintegrated. There's a serious cost/benefit analysis, and only in a "last...
Full answer by LevenTrek: https://movies.stackexchange.com/a/83814 (CC BY-SA 3.0).
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