Why did apple set a 90 day lock out to apple devices?

Why did apple set a 90 day lock out to apple devices? I bought my dad a new iphone 5s. He decided to give me his old iphone 4s but i cant download my purchased programs from my apple ID. I got a notification saying that the phone is associated/identified with another apple ID then automatically locked my apple id for 90days. I dont understand why they had to set a 90 day timer.