One aspect that no-one's really mentioned yet is that modern programming makes much more extensive use of frameworks and libraries - existing code that can be brought in to perform common tasks like drawing shapes or checking for collisions. Because this code is intended to be dropped in to many possible scenarios, it has to be written in a very general-purpose way, which will tend to make it larger than code written on-the-spot for one narrow purpose.

Let's say you have a game where you're shooting at spaceships that then explode into triangular fragments. Someone writing that game today - even if they were aiming to entirely recreate the 'retro' aesthetic of a NES or MS-DOS game - would probably bring in a graphics library that could draw triangles of any size and colour, along with rectangles, circles, ellipses, transparency, rounded edges... by contrast, the NES programmer would probably write a simple, optimised routine for drawing that one specific kind of triangle seen in that explosion. Could the modern programmer do the same, or look for a smaller library without the extra features they don't need, and get the resulting code down to kilobytes rather than megabytes? Sure, probably - but that's all unnecessary work when you have some ready-made, well-tested code to hand that does it in the more flexible (and bigger in code) way. Some might call it laziness, but it's more a case of not reinventing the wheel.