Surely a true follower of a religion is one who does what their Holy Book commands? If person A does as the religions commands and person B rarely does it, why is person A not the "real" follower?
I know this is TrueAskReddit, so you're probably hoping for an in-depth answer with lots of proof. This isn't one of those answers. Here's my shoddy attempt at one, minus the depth and proof.
The idiom "Can't see the forest for the trees" comes to mind. There are those who get so obsessed about rules that they forget the bigger picture, what the rules are all about -- in many cases, a "For Dummies" guide to building a healthy relationship with one another and The Creator. You can't really have one without the other. It's easy to read a book full of rules and say that you follow them. It's a lot different to take a library and say you follow all the rules. (which the Christian bible is... a collection of books from different sources written by different authors at different times written in various literary styles for different audiences experiencing different struggles)
Now, since this reply is pretty much devoid of proof, I'll give you another example:
Most people say that Catholicism has a lot of rules about sexual morality, correct?
Between 1979 and 1984 the Catholic pope at the time had a series of talks describing a way of thinking about sexuality that attempted to take the focus away from 'don't do this with your sexuality because God said it's evil,' and more on "Your sexuality is a gift and a reflection of the divine, and here's why..." These talks were assembled and called "Theology of the Body" and although the English translations of the 129 lectures are available online, most materials easily understandable by laymen such as you and I are not free.