Yes, if I am not mistaken, the idea behind that interest rate was to make the ecosystem more attractive for outsiders and then convert them in regular users. I don't think it was a success, though.

In my opinion, anything should be more profitable that curating. As you cannot get over say 10% APR on your curration, the HBD APR should not surpass this treshold. Otherwise it is an incetive to quit curating and use Savings instead.

The rate is quite flexible, it can be changed anytime to almost any value, it is just up to witnesses.