As I restore my phone, why does the internal memory become low?

[AC Question]

as i restore my phone.each time its internal memory becomes low

amusing karbonn a1+champ.i rooted it.using now link2sd.when i restore it after uninstalling all the apps.its internal storage for apps becomes low.suppose it was 60 mb then it becomes 40 mb and so on.i tried deleting the leftovers of apps but nothing works