Hussar
Legend
Keep in mind that a lazy DM in, say, 1981, would have had access to the following, beyond the core books (and basic and expert D&D rules)
B1 In Search of the Unknown
D1-2 Descent into the Depths of the Earth
D3 Vault of the Drow
S1 Tomb of Horrors
G1-2-3 Against the Giants
B2 The Keep on the Borderlands
S2 White Plume Mountain
T1 The Village of Hommlet
C1 The Hidden Shrine of Tamoachan
C2 The Ghost Tower of Inverness
Q1 Queen of the Demonweb Pits
S3 Expedition to the Barrier Peaks
X1 The Isle of Dread
A1–4 Slavers Series
B3 Palace of the Silver Princess
I1 Dwellers of the Forbidden City
L1 The Secret of Bone Hill
U1 The Sinister Secret of Saltmarsh
X2 Castle Amber
PLUS Deities and Demigods, the Fiend Folio, the World of Greyhawk Folio,
PLUS PLUS Monthly issues of Dragon, which had been in print since 1976 (since 75 as the strategic review)
ADD, from even earlier, licensed Judges Guild products.
They may have been industrious with their games, but DMs also still had some help.
True, but, this is what three YEARS into the life cycle of 1e. How much of that would have been available in after the PHB was released? I mean, after 5 months of 5e, you will have two complete 15 level adventure paths. That's about the equivalent of 16 modules. Plus web enhancements (now coming monthly), plus various other odds and sods. Let's see where we are in 2017 before we make this same comparison.