The Japanese industry is heavily built on people buying the same chapters plural times.

Its why they still do "every store that sells this volume has a unique original art" model. People will sub to X magazine or buy the chapters in tokens online, and then go buy multiple copies of the same volumes later to get all the extra goodies. And then the Limited Edition version later that has the figurines/shirts/etc bundled.

So its less digital has overtaken solid books and more like "online piecemeal has overtaken giant magazine subscriptions." Because rather than pay for the full Shounen Jump for a single series you can just pay a fraction for the one you care to read.