Fuel Selector: Why Only Left or Right and no BOTH?

[flytoboat]

Switching tanks in flight is ALWAYS a problem, and the risk it carries is not superstition. The question on the table is whether either "less than ideal" system (Van's, or the "Both") results in lower overall risk for a specific pilot. The "fix" is to pick the system of lowest risk after weighing the options.

Switching tanks in the low wing Pipers every 30-45 minutes was NEVER a problem while I was flying. What am I missing? Over 6000 RVs can't all be wrong.