It is a good idea to go in because:
1. It is an opportunity to gain some insight into her family. What is the atmosphere in the home like? Do the parents try to make you feel welcome/comfortable? How do they interact with each other? Is the home clean/tidy? etc.
2. A glimpse at the potential shvigger is a preview of what you may be married to thirty years hence!
3. It is also an opportunity to make a good impression. You never know, she may be the one who needs convincing and by going in and being a good ambassador for yourself you may just be recruiting her parents as allies at a later point. Beware that this can have the opposite outcome, so be careful!