Of course people are drawn to Robin Hood type characters, people living their dream on the edge of life etc. This isn't something new.
Heck.. people were fans of Walter White in Breaking Bad (myself included) and even though he became more and more guilty and unhinged as the show progressed people still found it in themselves to like him and forgive his actions (not counting that Walter started off as a Meth cook which in itself is pretty much appalling and Dominic Toretto is basically a petty thief to fund his lifestyle).
They are the bad boys who flaunt authority, give them the middle finger and live life "on their terms" which is something many of want to do but we are realistic enough to know that most of us would fail and in extreme cases would end up dead (heck.. driving like those guys in the movies would kill about 95% of regular drivers).
It is a fun movie series full of cool dudes and dudettes, awesome cars, music and stunts with huge logic and plotholes but it's the type of movie where you can turn off your brain (in fact it's mandatory) and enjoy it for 2 hours at a time.
And because of this i love this movie series and strangely enough it gets better movie by movie (my subjective opinion of course).