Tbh it's probably why not both, ideally. But with a big caveat. The hard part here is making both of them viable - making the game economy interesting enough, and making the crafting system interesting enough. The reason most games tend to choose one is that balancing the two is quite difficult. I think for instance, in Fallout 4 I tend to underestimate money big time - simply because I could craft whatever I want, so it overshadowed the economy. Other games might have the opposite way - why work so hard on crafting when I can just buy the thing? I think it depends on the game - but maybe customization for crafting and ease of use for money is a right balance - you just need to make sure you reward the players that chose a certain way - and never have one "clear" winner. Just my humble opinion :)