The 80s were a period of great diversity and hence progress. In that decade I used 6502 (BBC Micro), 68000 (ST), ARM (Archimedes), there were also Z80 and early x86s. There were many approaches to systems design, many competing ideas, what you might call a Cambrian Era (http://en.wikipedia.org/wiki/Cambrian_explosion).
By the 90s, things settled down. People (as in, "end users", the people who ultimately pay for software) had figured out what they wanted to do, which is forms (screens for entering data into a database) and reports (screens for getting it out again, nicely formatted). Messaging, as in email/IM, is just a special case of this (and today, FB et al are just forms and reports). What was "good enough" for this was an x86 (which happened to be running Windows, but that's irrelevant IMHO) and that became the lowest common denominator. The diversity was still there in the form of the Unix workstation market but they spent all their strength competing with one hand and trying to standardize with the other. Meanwhile the relentless march of hardware continued on, Intel was swimming in cash and none of the Unix vendors noticed, they were all preoccupied. Now there is one architecture to rule them all (tho' ARM still clings on).
And we the developers are to blame. We fell into a comfort zone. The users wanted forms and reports, and that's what we gave them. Then the hardware gave us more power and we gave them bells and whistles too. But really, that is solved, has been solved for 2 decades now. Nearly everything we do with computers now, could have been done in 1990, and what they did then, we do the same now, except arguing over syntax, which of a dozen functionally equivalent "frameworks" to use, which ALGOL-derived language to use, which desktop to use with slightly different-looking widgets that do the same thing, etc etc etc. All this is just procrastination. None of these things matter. But comfort zones are, well, comfortable. It's like we climbed a small hill and stopped to enjoy the view because we are afraid of the mountain we have to climb still.
There are a few tantalizing glimmers now, of the "next level". But we wasted 20 years dicking about.