If I was a hoglet, and due to leave the nest, I would want to explore the world – so I think that might be the mentality of why they might leave.
I think I would be more concerned if they spent all summer in just one nest, and didn’t even explore your garden, I’d want to tell them that they might be missing out on some exiting stuff.
The problem is, we constantly worry about them, their safety, so we would prefer if they stay safe and secure in the nest we have provided for them, but I don’t know if that would be beneficial for them long term.
I’m sure, as Nic said. some will return, now they know where some tasty food is.
Problem is, you aren’t likely to recognise them when they get bigger and return, so you’ll be left worrying if they are ok – but I feel on the whole, it’s probably best if they go off and explore, see what’s out there.