If you are going to be doing some big trips in the future not only will a credit card be of great use, in some areas of travel it will be close to vital. Car rental without a credit card is problematic, many hotels require a credit card to hold a resèrvation,which doesn't work with debit cards, and its also very useful in case of fraud.
If you have a debit card which is compromised, then the money that is stolen goes immediately out of your bank account. This is problematic for two reasons, one, its your money and its gone and you have to get it back, two, it tends to affect other things, such as mortgage payments and the like.
In contrast, if you have the same with a credit card , no money has left your bank account, and the charges can be wiped off without any money leaving your account.
If you are abroad somewhere perhaps with contact back to your bank difficult, the last thing you want is a wiped out bank account. With a card, your bank account is "insulated" from fraudulent activity.
Chosen carefully, there is no downside to gettinga card associated with an airline, and neither is there any downside, even if you don't go out of your way to get tickets that collect them, to join the frequent flyer schemes, its cost free.
BTW, one thing that many people don't understand, they are frequent >>flyer<< schemes, notwithstanding the fact you can get miles for credit card purchases and so on, you only get miles ina scheme fir flying, not for just purchasing the tickets. The miles the fire come into use after you've flown. So, it might be for example, that after a few long distance big trips, you'd have enough miles for something like, for example, free flights to Europe or Hawaii or ten Caribbean.