Printing a single copy when it is ordered sounds like a minor technical development and has restructured a substantial part of publishing.
The old constraint
Offset printing has high setup costs and low unit costs at volume.
Which required print runs of thousands to be economic.
That capital requirement was the gate that defined who could publish.
Digital printing economics
No setup cost, higher unit cost, viable at a quantity of one.
Which removes inventory risk entirely.
Unit costs have fallen enough to make it competitive for short runs.
The backlist effect
Titles that would have gone out of print remain available indefinitely.
Which has substantially expanded what is purchasable.
It has also complicated rights reversion clauses that depended on being out of print.
Quality
Print quality has improved to the point of being difficult to distinguish for standard formats.
Which was a genuine limitation in earlier years.
Colour and specialist formats remain more constrained.
Distribution integration
Print on demand integrated with retailer catalogues.
Which means a title is orderable everywhere without existing anywhere.
Discount and returnability settings affect whether bookshops will order it.
Bookshop resistance
Many independent bookshops are reluctant to stock print on demand titles.
Which relates to discount levels and to non-returnable terms.
Authors setting these parameters affect their own retail availability.
Environmental effect
Producing only what is ordered eliminates the overprinting that produced pulping.
Which is a genuine improvement.
Shipping individual copies has its own footprint.
What it enabled
Independent publishing at scale, permanent backlist availability, and academic and specialist titles that could never justify a print run.
Academic publishing
Specialist monographs viable at very small print quantities.
Which has kept scholarly publishing possible in narrow fields.
Library purchasing at institutional prices supports these economics.
Hybrid publishers
Services combining author payment with publisher functions.
Which range from legitimate to exploitative.
Author organisations publish criteria distinguishing them.
Regional printing
Printing close to the buyer reduces shipping.
Which is how global availability is achieved without international freight.
Print facilities on several continents serve the major platforms.
Cover and interior requirements
Technical specifications differ by printer and format.
Which is where independently published books frequently show their production.
Templates and professional formatting address most of it.
The structural change
Publishing became a service anyone can purchase rather than a gate anyone must pass.
Colour and specialist formats
Colour printing costs substantially more per unit.
Which limits viability for illustrated books.
Photography and art books remain difficult to produce economically this way.
Distribution settings
Authors choose discount and returnability when publishing.
Which determines whether bookshops will order the title.
Default settings are frequently unattractive to retail.
Quality control
Variation between print facilities.
Which authors discover by ordering proof copies.
Ordering a proof before approving is standard practice.
Effect on publishers
Large publishers use it for backlist and for short runs.
Which keeps titles available that would previously have gone out of print.
Reversion clauses in older contracts did not anticipate this.
The net effect
More titles available, less waste, and a permanently lower barrier to publication.
Why it mattered more than it sounds
The capital requirement for a print run was the gate that determined who could publish at all.
Removing it did not make publishing easy, and it did move the difficulty from access to attention, which is a completely different problem with completely different solutions.
Author copies
Buying your own book at production cost.
Which enables direct sales at events without inventory risk.
Direct sales carry the full margin and are a meaningful income source for some authors.
Ongoing availability
Titles remain purchasable indefinitely rather than going out of print.
Which changes what a backlist is worth.
Effects on secondhand markets
Permanent availability reduces scarcity value for recent titles.
Which has changed used book pricing for anything still in print.
Genuine out-of-print scarcity has become rarer.
Short-run offset
Digital and offset printing now overlap at moderate quantities.
Which gives publishers a genuine choice on print runs of a few hundred.
A closing observation
A printing technology removed the financial gate that had defined publishing for five centuries, and the industry adapted without much acknowledgement that it had happened.
What replaced the capital barrier was an attention barrier, which is harder to cross and impossible to buy your way through reliably.
The practical consequence
Almost any book published in the last two decades can still be bought new, which was not true of any previous era.
One more thing
The technology also made academic and specialist publishing viable at quantities that would previously have been impossible.
A great deal of scholarship exists in print only because of it.
The summary
Capital barrier removed, backlist made permanent, waste reduced, and the difficulty relocated entirely to being noticed.
None of which was the stated aim of a printing technology.
All of which is publicly documented for anyone who wants to check it.