To A charedi a day of rest means, going to shul in the morning, having a nice shabbos meal and then taking a nap
To a Chiloni, a day of rest means either going to the beach and relaxing or going to the mall and hanging out , maybe going to a cafe, Seeing a movie or soccer game.
They are going to do these things anyway on their day off. Its better for them to do it on Sunday than Shabbos. Many Gedolim in Israel are in favor of Sunday off for this reason