PE Ratios are generally more important for investing than for day trading. Especially in an overheated bull market like we've had for the last many years.
But the trend is showing signs of weakness so PE becomes more important. Not only as an input for planning investments, but because it can indicate a shift from the hot growth stocks to more boring, solid companies. I'm a day trader myself so I don't really care about fundamentals like PE - I just trade the chart in front of me. But it it's a valid indicator of changing sentiment when you see the former divas losing their bullish shine.