You are incorrectly attributing the blockchain's transaction patterns to Bitcoin Core's default mempool policies. They think the blockchain 'reflects' these filters because the filters are actively preventing bad transactions from being included.

This is backwards causation. The mempool policies are purely local settings that only affect what transactions your individual node will relay or store in its mempool - they don't control what gets mined into blocks. Miners can set these filters to whatever they want, or ignore them entirely.

The real reason the blockchain resembles the default policy settings is much simpler: most people naturally create valid, reasonable transactions anyway. The blockchain looks 'clean' not because the filters are working to keep it clean, but because there wasn't much junk to filter out in the first place. The filters are largely redundant - they're rejecting transactions that most users wouldn't create anyway.