Without a reason to shop, consumers are holding onto their wallets. Back in June, Best Buy (NYSE: BBY) termed customers' reticence as "episodic." Without some event to drive consumers to stores, they were staying away.

"Episodic" can also perhaps best describe the faltering performance of Sears Holdings (Nasdaq: SHLD), which saw same-store sales decline at both its namesake domestic stores and Kmart. Comps were down 1.4% at Kmart and 2.8% at Sears domestic. Apart from the a government rebates-for-refrigerators program or some seasonal interest in air products, shoppers saw little need to visit. Total sales fell $93 million, to $10.5 billion, while losses totaled $39 million, or $0.35 a share, excluding certain items. Both numbers missed analysts' mark, even if the net loss was narrower than a year ago.

We're in the midst of the back-to-school season, the second-biggest shopping period, and later on we'll have the holidays. Investors can probably expect to see some bumps from those events, but the fallow time in between will be hard on broad-line retailers, and not just Sears.

Both J.C. Penney (NYSE: JCP) and Kohl's (NYSE: KSS) reported ugly outlooks for the coming months. Penney's lowered full-year earnings guidance to $1.40 to $1.50 per share, below the $1.54 that Wall Street had forecast, while Kohl's forecast third-quarter results at $0.57 to $0.63 a share, well below the $0.74 Wall Street was looking for. It also trimmed the high end of its full-year forecast.

As much as sales may be driven by episodic demand these days, it's also necessary for stores to try to create events to spur consumer interest. Even as mighty Wal-Mart (NYSE: WMT) suffered a slump in comps last quarter, its price rollback campaign is helping the discount giant to raise its earnings forecast for the year. Target (NYSE: TGT) has captured some of the sales flash normally reserved for Wal-Mart, but without the government doling out cash for energy-saving appliances what's a consumer's impetus to choose Sears (or Kmart) over their rivals?

Sears Chairman Eddie Lampert has only recently decided that investing in his stores and his merchandise is a worthy endeavor, a decision that may have come too late in the game. Its $150 tablet computer sale was more of a gimmick like its Christmas in July promotions, as tablet computing is quickly becoming a crowded field. Even Best Buy may put out its own branded product.

Even with Sears shares down more than 25% year to date, the stock is still trading at 25 times earnings, putting it at more than twice the valuation of Kohl's and Macy's (NYSE: M).

An "event horizon" is a term that scientists use for that point in space where matter is on the verge of falling into a black hole from which it can no longer escape. Cross over that line, and not even light can escape the immense gravitational pull. Sears Holdings' future is quickly approaching that threshold.

Best Buy and Wal-Mart are Motley Fool Inside Value recommendations. Best Buy is a Motley Fool Stock Advisor pick. Motley Fool Options has recommended a bull call spread position on Best Buy. The Fool owns shares of Best Buy and Wal-Mart. Try any of our Foolish newsletter services today, free for 30 days.

Fool contributor Rich Duprey does not have a financial position in any of the stocks mentioned in this article. You can see his holdings here. The Motley Fool has a disclosure policy.