If your flight delays and you are waiting around for hours just to be stuck on a plane for even longer is tiring, even though you aren't really doing anything! Especially if you have young children and are stuck there for 6 hours, or even overnight!
If you have a delayed flight of 3 hours or more then your airline has a duty of care to give you free food and drink vouchers for the inconvenience, and if your Delayed Flight is overnight, then their duty of care is to pay for you to sleep in a hotel near the airport, and also to give you the vouchers. Even if you have received these vouchers or/and been giving overnight accommodation then you can still claim flight delay compensation.
So, for example, if your flight has been delayed overnight because there was a technical problem with the plane and they couldn't fix it, then yes, you are eligible to make a claim. But if your flight was delayed 179 minutes due to a storm then you would not be eligible. Or if you were coming to London from Paris on a British Airways flight and the delay duration and reason met the criteria set by the EU then you could claim for the delayed flight. But you would not be able to claim delayed flight compensation if you are coming from India to Manchester on an Air India flight, even if the delay and reason was eligible.