It really depends on the market and how it's acting. For example last summer it was really easy to use the 8 and 21 EMA for the YM. I could simply (I stole this from
John Carter) buy on pullbacks to the 8 EMA. CL you could do with pullbacks to the 8 and 21. But now they almost seem irrelevant since both the YM and CL seem to range more than trend.
The 50 and 100 EMA were plotted for the YM and ES, but since I use the same chart for all daily time frames it shows up on the CL chart as well. They work well for support and resistance levels as you can see on the ES. For the CL I guess you could say they are just there as they haven't been needed lately. Although the 50 did provide great support.
But on a normal trending market, yes I would use them. Just like any "indicator" though, they are more of a guide.