These two contraptions, so similar in name, are different enough in function to allow for fewer regulations for the latter (firecrackers). Firecrackers are explosive devices who’s primary function is causing a lot of noise. Any visual effects, such as a flash or spark, are secondary to this goal. Firecrackers are lit, just as fireworks are and also contain an explosive compound wrapped in a thick paper exterior. While firecrackers are supposedly less dangerous than fireworks, they are still explosives and while they may not be intended for their explosive element, there is still a risk that this can cause as much, if not more damage, than fireworks.
A number have places have set bans against firecrackers specifically. According to Wikipedia.org, the following countries have done so.
Australia does not allow the use of fireworks or firecrackers by people who are not licensed pyrotechnicians except in their capitol territory. A permit is required where fireworks are not illegal.
In Canada, firecrackers are not covered under the ‘Explosives Act’ making them illegal to use, store, transport, or possess.
Mainland China has allowed the use of firecrackers since 2008 in most areas. This makes sense culturally since firecrackers are integral to the celebration of the Chinese New Year. Fireworks and firecrackers are illegal in Hong Kong, however.
In Indonesia, fireworks and firecrackers are not to be used in public during the Chinese New Year to avoid a conflict between the local populations of Chinese and Indonesians. Some metropolitan areas allow a limited usage, such as Jakarta and Medan.
Sweden, oddly enough, on allows rocket type fireworks. In 2001, firecrackers were outlawed here.
As you can see, the use of firecrackers differs somewhat from fireworks but depending on the culture, they are treated differently than fireworks.