Unusually being the key there. If you are just going to say yes to every time they ask to jump farther, it's no longer unusual. Also, that rule does not exist in a vacuum. It exists within the context of Page 6. To declare an action you describe what your PC is doing and then the DM adjudicates it. "I use athletics to jump farther" is not a description of what your PC is doing. It's a statement of intent, sure, but a description it is not. So you are breaking the rule on Page 6 if you accept that. That's fine, but it's effectively a house rule to do so.
Usually you jump feet equal to your strength. I never said I would allow it all the time and honestly, I don't use the jumping rules all that often in the first place. If I thought someone was abusing it, I'd discuss it with the player. But, if the character is being chased by zombies like in [MENTION=467]Reynard[/MENTION]'s scenario I'd allow it. I think it's more fun, realistic and a cleaner reading of the rules.
As others have pointed out, you don't have the corner on the truth.