Not all people will overspend on credit cards when they do not have the funds to repay their bills. However, by sheer probability, SOME of the people WILL overspend. When you don't have a credit card, by definition you can't accrue debt since you don't have a line of credit extended. One cannot say that not one single person with a credit card will overspend on their ability to pay.
Credit cards make it very easy for people to spend more money than they have and allows individuals to ignore the overall costs of the item in the long run. There needs to me more education for young adults about what the true cost of an items purchased with a credit card will be.
As a person that is currently tackling $15,000 in credit card debt, I assure you that credit cards encourage people to spend far more than they have. The credit card companies encourage and promote this behavior as well. I've learned to hate to Discover because as soon as I maxed out my card they started sending letters suggesting I apply for their home equity loan. I may have over spent but I think the suggestion that I end up losing my home to them is a bit over the top. I suppose there have been many people who have fell for this tactic...
Yes, credit cards encourage people to spend far more than they have, because they have the option to. If someone doesn't have credit cards, they have no choice but to live within their means. By having the option, a person can misuse a credit card and rack up personal debt.