You don't even need a credit card to have a high score since you can have credit in other ways (ex: auto loan, mortgage, etc). However, there are benefits:

• a particular card can give you cash back vs another card that can give you points you can use on airlines
• others have good deals at certain times of the year. For instance, a certain Discovercard gives you 5% cash back on Amazon purchases in the fourth quarter
• some cards give you more cash back on only gas or grocery purchases
• some cards are store credit cards like Home Depot

The general benefit of having multiple generic cards is that you increase your total available credit which means if you put on a large charge on a card, your credit score won't be affected since the total utilization is still low.