Comment by stevesimmons
12 hours ago
For Python, you can read the PEP documents - Python Enhancement Proposals - and see the discussion of what was suggested, pros and cons, work done to determine the preferred implementation, and the final decision.
It's pretty far back on my blog to-do list, but the key order guarantee that was solidified in 3.7 lost the opportunity for a further space optimization (for dicts where keys are frequently removed).