Well you can set a few options. One is to receive dividends at the intervals that Tenx determines and the other is to set your own amount when you want to get the dividends. By default every account would have the first option enabled and if anyone wants to change this they can do so in their account...
Why would stuck funds in their wallets be a problem?
Well, both things cost a lot of money. They would need extra customer support for all those users who experience problems, which is very expensive. If there is enough demand for these features, they will do it, of course. But the "just pay every token automatically every month to the same address" option is very cheap and doesn't need any support. Gas, of course, but gas is a huge deal cheaper than support-man-hours at the moment. And to keep Ethereum alive, it should stay that way.