Are you sure you're not just looking at prices that are adjusted for the split (Yahoo, for instance)? A company I hold (Gilead Sciences) split a few months ago, but if you look at a price chart, there isn't an interruption even though the split is clearly marked. (Look in the past six months; it split in January). However, you could also simply be watching companies that happen to not split, for a variety of reasons. This isn't a criticism, but rather just a consequence of whatever stocks you happen to be watching.
However, a quick search for information on stock splits yields a few articles (mainly from the Motley Fool) that argue that fewer companies are performing stock splits in recent years; the articles mainly talk about tech companies, and they make the argument that even the shares in Google and Apple have a high stock price:
Google and Apple aren't all that expensive by traditional valuation metrics. Google trades at just 15 times next year's projected profitability. Apple fetches a mere 13 times fiscal 2012's bottom-line estimates.
Keep in mind that these articles are a bit dated in terms of the stock prices, but the rationale is probably still good. Similar logic could apply for other companies; for example, I've held Panera since May of 2009, and the price has climbed by almost a factor of 4, yet no split is in sight.
The articles also make the point that stock splits were traditionally seen as bullish signs because:
Companies splitting to bring their share prices back down to more accessible levels were optimistic in building those sand castles back up.
One could make a fair argument that the overall economic climate isn't as bullish as it used to be, although I would only be convinced if data could be gathered and tested. A stock split can also raise the price of a stock because if small investors feel the stock is suddenly more accessible to them, they purchase more of it and therefore drive up the price. (See the Investopedia article on stock splits for more information). Companies might not see the necessity in doing this because their stock price isn't high enough to warrant a split or because the price isn't high enough to outprice smaller investors.