There is no reason for Disney to expect that some members will forfeit points. If the owners were savvy enough to buyh, they should not have purchased more points than they can use by banking/borrrowing.
However, there are always some points that will go to waste, whether because the owner has passed away and the contract is tied up in court, or because of a diverce, or simply a careless owner who forgot to bank. That is simply normal.
There is little direct benefit to Disney if an owner lets points expire. Sure, they may get an extra room to rent, but in todays market, with slower than average cash rentals, that is hardly a plus.