Fannie Mae is back at the government trough, asking U.S. taxpayers for another $4.6 billion to help the mortgage giant stomach a $2.4 billion quarterly loss -- and intimating it may need more down the road.

With this latest request, Fannie Mae and its sister firm, Freddie Mac, will have borrowed about $188 billion since the two were taken over by the U.S. in 2008. The eye-popping amount will surely renew calls for the U.S. to finally show Fannie and Freddie the door.

But the mortgage market is so incredibly weak, and so reliant on the two companies, that the day of reckoning is probably a long way off. Private issuance of mortgage-backed securities -- a type of bond used to finance real-estate loans -- is down more than 99 percent since its peak before the financial crisis, according to a Bloomberg analysis.

There's no shortage of ideas about how to get Fannie and Freddie off the government dole: Privatize! Shrink their portfolios! Shut them down! But the uncomfortable truth is the companies, which account for about 60 percent of all outstanding mortgages, are critical to a functioning housing market. Without them -- or with a smaller version of them -- an already tight credit situation would get tighter still, leaving millions of borrowers unable to get home loans.

At a time when housing is weighing down the broader recovery it's unlikely -- and unwise -- to neuter the two things that are keeping the housing market from slipping into an even deeper abyss.

(Deborah Solomon is a member of the Bloomberg View editorial board. Follow her on Twitter.)

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