Availability of money teamed with personality, the ability to delay gratification and that old sense of responsibility again. I didn’t grow up in a wealthy family and my dad gave me a little bit of money each day to spend. I spent it every day. I was never a saver. My dad on the other hand was and had no option but to be frugal and careful with money. I remember one day, coming home and there was a radiogram (god how old am I!!!) in the lounge room and he was playing with it and was like a kid with a new toy. The next day though, it was gone. You know, I really think he had impulse bought it and then decided he had more important things to spend his money on and sent it back. It was never mentioned.
In my first marriage, I had to be frugal and careful and I was younger and had bills and things to pay. I didn’t spend money on clothes I didn’t need or cosmetics I didn’t really have to have. I was very careful with money and paid off bills in advance so that I knew where I was financially. Now, I don’t have those constraints and I can be quite the spender. I don’t have to worry so much about things financially. I am not silly with money, but I don’t deprive myself.
I think the answer is in a combination of elements, personality, upbringing, sense of responsibility and current needs. Not sure if that really answered your question though. I don’t think there is a definitive answer.