But the USB charger manufacturers could do better by shutting down the output should arcing/sparking be detected. We already have this for 120V AC supplies, and it should be doable for 5V DC.
A poor connection at a plug can (or will?) cause a hot spot without arcing, and for a long thin cable a short may not even trigger the overcurrent protection of a high power charger.
Best to buy a cable with a decent 'AWG rating' eg 24AWG, either from a reputable brand like Tronsmart, or a specialist supplier, in the UK there's Kenable: