Ian, introduction of enlargers and enlarging era are different . To my understanding enlargements at the turn of the century had a nihil share amongst the number of prints made.
And at least over here type 120 cameras were sold post WWII in masses, as they could be made in simple ways and still yielded prints for albums being made at lesser cost than enlargements from 35mm film.
Judging by the number of different enlargers avaialble in 1898 and also papers for enlargements,nd companies offering enlargements as well as Carbon and Platinum prints, hand colouring etc, toning etc I think you're wrong. Of course the mass market would have been small enlargemnts and contact prints, but that remained the same in terms of small prints to what we have left today and larger prints have always been far fewer.
However when it comes to using the older higher end roll film cameras your going to have more serious photographers and a much higher proportion wanting enlargments. One 1898 advertiser G. W. Secretan in London offered a trade printing and Enlarger service, established 20 years. Another Myers and Frost, The Manchester Photo Enlarging Compy, established Over 30 years, I'm not suggesting they'd be enlaging for over 30 years rather thats how long they'd been established.
Also by 1898 Ilford offered a range of four Enlarging papers as well a POP as did many other UK manufactuers. Ilford papers 34" wide and 20ft rolls indicates there was quite a marke, not "Nil". They'd already sold 70,000 copies of "The Ilford Manual of Photography" it covers enlarging (I have a copy), and had a monthy magazine The Ilford Journal with a circulation of 35,000. There were many other companies making enlarging papers here in the UK, Austin Edwards, Cadett & Neal, Elliott & Son (Barnet), Gem, Imperial,Ilford, Marion, Mawson & Swan, Paget, Wellington & Ward, Wratten & Wainwright and I've missed a few, also enlarging papers were imported and sold by Eastman Kodak and European manufacturers. This was around the time George Eastman first approached Ilford with a view to buying the company but they weren't interested so he set up his own factory here.
Interestingly Ilford offerd an Bromide Opal, a forerunner of Oplaline, a bromide emulsion on Opal glass in sizes up to 15"x12" so by 1898 there's a surprising maturity in the market.
Ian