Why does the pattern lock exist?
I am no longer able to use the pattern lock since I've enabled fingerprint recognition.  However, when I did use pattern lock I always used all nine dots and I disabled all haptic and visual (line drawing) feedback.

I could draw my shape in a fairly fluid motion and the latter movements wiped across the earlier, so judging from the fingerprint smear wouldn't necessarily be obvious as to the shape I drew.  Additionally, I'd cross back at the end over areas I've already touched.  Without the haptic feedback, someone might have a difficult time knowing which dots were drawn over the first time and which were done to throw them off.

My best protection, however, was to take a quick glance to see if anyone was looking before trying to unlock my phone.  If someone is clearly watching you and is interested in breaking in to your phone then you're going to have a hard time maintaining complete security regardless of your lock method.