Two things: lack of having a clue and perverse incentives. The first leads to endless piles of barely functional code; the second rewards that.
The 'real' programmer that spends a month on a long term maintainable chunk of code with a well defined API and some documentation to go with it in a few hundred lines of craftmanship will be at a disadvantage to the person that creates an unmaintainable mess half the time and that is promoted away for being so great at 'getting things done' before they have to deal with the mess.
The 'real' programmer that spends a month on a long term maintainable chunk of code with a well defined API and some documentation to go with it in a few hundred lines of craftmanship will be at a disadvantage to the person that creates an unmaintainable mess half the time and that is promoted away for being so great at 'getting things done' before they have to deal with the mess.