There are those for whom this is offensive and for them, they need to wear what they feel appropriate to bed for whatever reason they deem appropriate. If it is related to a disordered attitude towards their own body, they should work to correct the disorder. If it is related to just either their modicum of modesty or wanting to be extra warm, go for it.
But at risk of giving too much information, when my wife and children are gone, I usually lay on the couch in my boxers eating ice cream or potato chips watching three sporting events at a time. After gourging myself and probably inspired by the sports I watched, I go down in my boxers and run on the treadmill. When I’m done, I go take a shower, walk naked to my bed and go to sleep.
If my wife and daughters knew what I did in their absence, they’d think it gross. For their sensibilities it is. For me, it is just an evening of me being the simple guy I am. After writing this, I am kinda looking forward to their next trip to see my daughter at college.