The reason is, it is easier to forget about it than to take care of something no one wants. The hoa's should accept deed backs to prevent this but for the most part they don't. This is a problem created by them, not the owner of the timeshare. Don't blame the player, blame the game.
What you propose is that everyone with a timeshare go though the arduous task of exiting a timeshare after they pass which is ridiculous, imo. The bottom line is all liabilities , including a timeshare, are gone, when you pass away with no assets to pay the liabilities. When your assets are in a trust they are removed from your personal assets. You feel that placing a worthless liability, which include most timeshares, into the trust so that the trust beneficiaries will have to deal with it is better than leaving it as a personal asset outside the trust where no one has to deal with it.
Your way is good for the hoa. My way is good for me. Obviously, I would choose my way as it is legal and very easy.
Calling others names like deadbeat who would choose the easy route, which actually made me smile, means you know the process works in the way I said. In fact, I'm naming it dead beat style and I'm sure my attorney will grin too. Dead beat style is a suitable name because, I'm dead and I beat the system, lol.
Bill