uml - Understanding why the extends arrow points in the opposite direction - Stack Overflow

In class diagrams I typically see something like ClassA extends ClassB where the arrow head points to ClassA. Example, here. This has always confused me. Why is the arrow head not pointing to ClassB?

oop - Explanation of the UML arrows - Stack Overflow

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oop - Explanation of the UML arrows - Stack Overflow

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tikz pgf - Draw arrows from multiple nodes to one and join with a common line - TeX - LaTeX Stack Exchange

uml - Understanding why the extends arrow points in the opposite direction - Stack Overflow

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