When I joined an east coast computer company in the mid-80s, ties all the time were already gone for a lot of engineering positions (though more senior engineers and managers still tended to wear them). Suits were pretty standard for marketing for marketing and other business roles.
Around the time you say, casual Fridays came in. The funny thing is the CEO got annoyed at one point because a lot of the engineers felt they need to underdress relative to the business people who were now dressing business casual on Fridays and increasingly most days.
I'd say that over the next couple decades, things got more and more casual to the point where ties, much less suits, are pretty uncommon in settings where not wearing one would have seemed out of place 25 years or so ago.
At trade shows, as I recall, at some point in the 90s, IBM booth staff showed up at one big show wearing branded polo shirts rather than suits. At which point, most everyone else went: If IBM isn't wearing suits, I guess we don't need to.
