I'd have thought it pretty much has to be a combination of

• laziness
• impatience
• humility (i.e., thinking others can make better than oneself)
• habit

I don't think laziness and impatience are necessarily vices in this sense. Sometimes you have very good reason to want something quickly. Sometimes you have very good reason to want something without having to spend a lot of effort on it.

Making a batch of cookies takes maybe an hour of work plus a couple of hours of delay (depending on exactly what sort of cookies). More, if you don't have ingredients to hand. So if you're in WANT COOKIES NOW mode, or if you don't enjoy making cookies, or if you have more important things to do, it's not hard to see how getting them from a shop might seem preferable.

Personally, I love making tasty things and at least 90% of the cookies and cake I eat I've made myself. On the other hand, I have no interest in making clothes or bookcases or houses or cars. I do enjoy making software but am orders of magnitude short of having enough time to make better word processors and web browsers and operating systems than the Usual Suspects. I don't see that any of this is terribly surprising.

There's another answer, which I think is answering a slightly different question from yours: Because it's more efficient. Economies of scale, specialization, etc. -- This doesn't exactly explain why people choose to consume rather than produce, but it explains why society "chooses" to centralize production as it does and why that's a pretty good choice overall.

(Incidentally #1: yes, it was deliberate.)

(Incidentally #2: I am pleased to report that yes, the internet has already invented the term ad mominem, which means just what you think it does.)