Scenario:
You want Ambidexterity. You REALLY do... but you just made 3rd level, and your dexterity of 14 isn't QUITE high enough. Your DM won't let you take the feat without the 15 dexterity, and rightly so because you don't have the attribute score to learn it.
Here's what you do.
You borrow the rogue's gloves of dexterity for a month, and you get someone to teach you the feat. Your dex is 16 now, more than enough.
Once you've got it down, you hand the gloves back to the rogue, and lose access to the feat.
When you make 4th level, you put your stat point into dex, and there you go... you 'saved' your feat, and you didn't have to break the rules to do it.