"Seven shuffles are needed to get a perfectly-random deck" is something of an urban legend among card players. The magic number "seven" came from a mathematical exercise, where the authors made a mathematical model of shuffling and invented a definition of what "random" meant within the context of the model. It turns out that even seven shuffles aren't enough to create perfect randomness within that model, and in fact perfect randomness can't be obtained with any number of shuffles within that model. So they further invented a definition of "sufficiently random", and determined that seven shuffles would be sufficiently random.
Again, within the model.
So "you have to shuffle seven times" is not only true only in theory, it's true only according to a particular theory which isn't necessarily valid, as it contains assumptions which may not be valid.
In the real world, riffle-riffle-box-riffle-cut will be more than sufficiently random for any practical purpose to be encountered at a card table for any game that any human being is ever going to play using a deck of cards. In some cases, it might be advisable to wash the cards occasionally, or in a few cases before each deal.