There are solutions for battery safety with Li-Ion battery types. It's just these cheap products are not using them. They use the cheapest batteries which also have the least safety. Then they use the cheapest charging components which again increases the hazard. Charging faults are a common cause of Li-Ion battery fires.

Safer Li-Ion battery types are commonly used, but may be heavier and/or more expensive. For example the safest Li-Ion battery is the lithium iron phosphate type (known as LiFePO4). It's quite safe against fire, but it's heavier and more expensive. Next safest is the lithium manganese iron phosphate type (known as LMFP). It's considerably safer and still has the weight advantage, but more expensive. That type is used a lot in cars and home energy solutions.