Well, of course. Sometimes its such a pain in the a$$ to get money out of your bank account that if you can't buy it right there you don't. Hence why, as a teenager, before I had ATM or credit cards, I didn't carry anymore cash than needed for the task at hand.
Not if you only use a bank debit card. If there isn't any money in the bank, you can't spend it, unlike a credit card. I very rarely use cash any more. It doesn't make sense to go all the way to an ATM to pull out cash, when I can use the very same debit card at the store & money comes from the same account. As a result of rarely using cash, and rarely receiving change from purchases, I haven't been able to fill in very many o the state quarters on the boards I purchased for my kids.
BTW, I pay all my bills using my computer, so I also very rarely use checks.