Cutting Across The Grain

I've been told all my life to cut meat "across the grain", but like most advice it doesn't really stick until I know why it's the right thing.  Seemed like cutting "with the grain" was easier, and it is, but cutting "across the grain" makes the eating easier, which is certainly the better tradeoff.  Now that I know why, I won't have to be told again.

https://www.thekitchn.com/heres-exactly-how-to-slice-meat-against-the-grain-and-why-you-should-be-doing-it-meat-basics-215798