[foo_barrio]

Perhaps the repeated insertions/removals did clear off any light oxidation or slightly reposition the contacts?

[conductr]

I'll never believe it. Blowing was required and technique mattered.

[aidenn0]

Insertions and removals did work well on the Famicom, but not so much on the NES; the famicom had a typical edge-connector while the NES had a zero-insertion-force (ZIF) connector.

The pins would be repositioned with each insertion and you had to hope that all 72 pins made a good-enough contact. If the 10NES made poor contact you got a 1Hz reboot loop. If other pins made poor contact the game would kind-of sort-of work until it crashed.