Exactly, they want the perks not the responsibilities. Whilst it would still be sad if they didn't want to turn up to remember a member of their family, the fact is the former King still receives considerable income and benefits from the state. Not turning up at so many events just keep destabilising the monarchy and creating chatter and talk about the family rather than the crown. They should attend, firstly because they want to but of not that then they should turn up because they are being paid.
I guess you could see the income King Albert receives from the state as a pension. In that sense, it comes with no attached work obligation.
As I see it, King Albert is now retired and, therefore, he is not obliged to attend any official event. My problem with him not attending is actually that it was a memorial for his late brother, whom he grew up with and who supported him for most of his adult life before Albert became king himself. I can't imagine that Albert's relationship with his brother was so bad that he would choose sailing on the Italian coast over taking a day to remember the 25th anniversary of his passing.
Or maybe, as some posters hinted, Albert's issue is not really with his brother, but with his son.