Credit and debit vs multiple cresit cards

I don't want to come off as dumb, but I have only been using just my debit card for a few years (I'm 19) and have just decided to get a credit card to start building up my credit. My question is why should I get multiple credit cards, as opposed to just one credit card and a debit for all other purchases. Is it just the rewards and points that are the benefit? I plan to keep my utilization low anyways by using my debit for a majority of purchases. I also don't need to make any large purchases because I have money saved up and use my debit.

I guess my main question is, other than rewards, what would the benefit of mutliple credit cards be in my situation. Thanks!

*sorry for typo in title