You still can. You just have to convince investors that it's worthwhile to do so rather than relying on coerced collections from taxpayers.
$15B is a staggering amount of money. However, when you're a government agency, you lack any means for rational economic calculus--$15B becomes chump change.
Not, alas, me. I am old, tired, cynical, and sick. And disillusioned, as you may be able to detect.
--Boris