Funny thing---for all the flying I did in my younger days, I never once saw "check fuel level" on a checklist. "Boost pumps on"? Sure. "Mixture full rich"? Naturally. I guess "check fuel gauge" basically was assumed.
Besides, it's almost an article of religion to keep full tanks to prevent condensation and water contamination. And checking for water contamination is on the pre-flight "walk around" checklist.