The obligation for confession, at least,once a year (if one is in the state of mortal sin) is not a part of the Easter Duty, which is, that after one receives his first Holy Communion, he/she must go to communion at least once a year, DURRING THE EASTER SEASON, (from Ash Wednesday to Pentecost Sunday). The obligation for confession can be any time of the year, but should be as soon after one commits the mortal sin as possible.
As far as the Sunday mass obligation: most of us need that little push to make sure we continue to take a day to worship our Lord. Without the obligation we tend to get complacent. Just think of how many people that you know who don’t take the time to vist, or call, or write to thier parents - even months and years at a time. Not because they don’t love them, but because it’s not a priority. The obligation that the Church places on us reminds us that worshiping God is THEE priority. How many tend to FORGET(?) that there is also a rule of NO SERVILE WORK on Sundays?