If you want to have a successful LSAT test day, you need to learn to diagram. There are lots of ways I could say the same thing: Only if you learn to diagram will you succeed on LSAT test day, for example. Or: no one who succeeds on LSAT test day doesn’t learn to diagram.
One of the reasons diagramming is so great is that it lets you get all these statements down to the same logical structure:
Succeed on LSAT test day → Learn to diagram
Conditional statements such as the above are all over the LSAT. Many Logical Reasoning question types are chock full of them. Grouping games, especially the In and Out variety, often have nothing but conditional statements as rules. And conditional rules pop up not at all infrequently in ordering games as well.