Hamsters in pet trade cages are frequently housed in inadequate enclosures. European minimum cage size standards and welfare science evidence support much larger provision than is typical.
Hamster welfare requires large enclosures with deep substrate for burrowing (at least 30cm), solid-floored wheels, hiding material, and appropriate social housing (Syrian hamsters are solitary; dwarf hamsters are social). RSPCA guidance substantially exceeds typical retail cage size.