When consumers spend less, businesses in the aggregate sell less of everything, because every dollar spent by a consumer is a dollar earned by someone else -- usually a business.
Before the financial crisis, consumers borrowed aggressively to finance consumption, like drunken sailors... but unlike the financial sector, they never got a bailout. They were forced by the circumstances to follow Steve Martin's advice from Saturday Night Live: "don't buy stuff you cannot afford."[2]
Are we really that surprised that many consumers are reluctant to borrow and/or spend like before the crisis?
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Edits: modified first paragraph to convey what I actually meant to say, in response to ctl's comment. The original paragraph was poorly written. (Thanks for pointing out the inconsistency, ctl!)
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[1] http://www.npr.org/blogs/money/2009/02/household_debt_vs_gdp...