The transition from kilobytes to megabytes is not comparable to the transition from megabytes to gigabytes at all. Back in the kilobytes days, when the engineers (still) had to manage bits and resort to all kind of tricks to somehow make it to something working, a lot of software (and software engineering) aspects left to be desired. Way too many efforts were poured not so much into putting the things together for the business logic as were poured into overcoming the shortcomings of limited memory (and other computing) resource availability. Legitimate requirements for software had to be butchered like Procrustes' victims, so that the software could have a chance to be. The megabytes era accommodated all but high end media software, without having to compromise on their internal build-up. It was the time when things could be properly done, no excuses.

Nowadays' disregard for computing resource consumption is simply the result of said resources getting too cheap to be properly valued and a trend of taking their continued increase for granted. There's simply little to no addition in today's software functionality that couldn't do without the gigabytes levels of memory consumption.