heck, it could even be more than 4-6 babies.
yes, babies are cute... but they don't stay adorable babies forever. they turn into feisty, hormonal teenagers and then become adults like the rabbits you already have.
it can be hard to find homes for all of them. even if you arrange homes ahead of time, people sometimes back out. if you don't have new homes for them by 12 weeks old, you'll have to start making or buying extra cages because you'll need to keep them one per cage.
they'll eat a TON of food, go through a lot of bedding/litter, make a lot of messes...
they'll ALL need 4-5 hours a day outside their cage, and after 12 weeks old you can't let them out together any more (unless you spay/neuter them, then you can bond them into pairs).
you don't know if they have genetic problems to pass along to their babies.
breeding just to make cute babies is a really bad idea.
I bought a hamster last October because she got pregnant at the pet store and I felt bad for her. she had 12 babies (rabbits can have that many too, by the way, though it's not very common). her babies were ready to go to new homes by December. I found homes for some, but I STILL have six babies left, which means six cages to clean and six mouths to feed (actually, eight cages and mouths because I still have the parent hamsters too). I honestly almost wish I'd left her there and let them ship her back to the hamster mill - caring for her babies and finding them homes is WAY more work than I thought it would be. bunnies are even harder than hamsters - they cost more, eat more, require more space and are harder to find homes for.
a rabbit is a TEN YEAR commitment - do you honestly know six or more people willing to make that commitment?