Because I don't have four years to get something done, that doesn't do what I want when I finally get it, if it even works at all, and that I can't fix myself.

Okay, that was extreme, and if you think I was talking about programming, it's because you have a guilty conscience. ;-) It actually applies to all interesting fields -- programming, engineering, management, classical music composition, etc. Those fields don't even know what their best practices are, and acknowledge that things take too long and can't be managed. No manager would say: "Our programmers have best practices, so the work will be done next week." Why should scientists have such faith?

Meanwhile, do you trust Maxwell's Equations, Darwinian evolution, quantum mechanics, etc.? How did we establish the physical constants to mostly better than 8 digits of precision? Science has somehow figured out how to make progress despite the messy business of research.

For me, it's not that I "have" to do programming, but that physical science has been computation driven since before the 1940s. Programming is how I think and work. With apologies to Richelieu, "programming is too important to be left to the programmers."