Denied for 3 credit cards - “insufficient credit history”???

Okay, now I am EXTREMELY confused. I have a 756 Equifax/768 TransUnion credit score, with 2 credit cards, and a credit history of 4 years, 5 months. I have been seeking to apply for a new credit card, but every single one of the 3 cards that I have applied for have denied me for “insufficient credit history”. Is my credit history really that insufficient?? I don’t understand.