Technology changes and adaptation to individual play styles, not to mention a certain amount of marketing have changed the world. Hybrids have supplanted many of the higher lofted woods and lower lofted irons and drivers are far beyond 1 woods now. If Vokey had 1 bounce option at just 48-52-56 wedges, the sets may still be around. Depending on how often you use full swings, prefer a different feel, different bounces for different ground and bunker conditions, irons and wedges are really different uses. So I don't miss the sets and glad I don't have to buy a 3I-PW or 4I-GW anymore. I have 6-9 irons, hybrids, and wedges. Using 3 different shafts across these. They work better, for me.

Gordon, the first set of woods I purchased were 1-2-3-4, so I do remember those days.  I last bought a set of irons that came 3-SW in 1988 in Atlanta.  Those were Ram Tour Grind Axial that I bought used, and had to order a replacement PW from Ram because the previous owner had not included the PW when he traded in the set. 

As for your question about when this change took place, I think it's the '90's when the metal woods started really taking over.  Investment casting in the '70's probably helped, since now manufacturers could make a wider variety of clubs for less cost.

I remember 1-3-4 wood sets back in 1972.  Irons came in 2-PW.  I think sand wedges were about 57 or 58*. I saw quite a few Sure Out wedges at the Country Club.

Starter sets were 1-3 and 3-5-7-9 irons (I had 1-3-4 and 3-5-7-9; I bought a Haig Ultra Dual Wedge for $12 in 1972 and had in my bag until 2006). 

The rage at the Country Club (St Charles) was a BH 6 wood.   What hasn't changed is people still struggle to hit a 3 iron.