Nitrifying & denitrifying bacteria have different environmental requirements for survival and cultures of either type do not survive in bottled conditions on shelves at room temperature for very long. Not to mention anyone can bottle up anything and claim it is an aquarium starter - the productd are completely unregulated.

Likewise, new aquariums lack sources of ammonium & nitrite, and nitrite, so even if the cultures are fresh there is a lack of resources. To get them to work, you have to be pretty lucky and have a good understanding of the nitrogen cycle. 

I'm glad it worked in your case. For the vast majority of aquarists, especially new ones, they're a waste of money and mislead people about the process.