This is very true. One reason people find nests and think they're abandoned.I have had rabbits have their babies in the middle of my yard with 7 dogs. A complete nightmare. Mom only came once a day to feed, other then that they stay away from the nest so they don't attract predators. They are nearby but not on the nest.
Mothers only come to babies when they need to eat and that is only once or twice a day and only for a minute or two.
It is for their own safety.
Never heard of a mother providing any defense for their young while in the nest. If something finds them moms will sit by and let them all be eaten. Sad but they will live on to produce another litter rather then risk losing their own lives too.