That's because the average consumer is generally unaware or apathetic of all the negative aspects of DRM - until it inconveniences them massively - and it's to the advantage of the companies that they be kept unaware. The convenience aspect is appealing but you can have even more convenience without DRM. I don't have to "lug around physical books either"; I have a few hundred DRM-free PDFs on my laptop which runs a free and open-source operating system, and I can read or copy between devices or do whatever else I want with those files, whenever I want.

Let's not forget what could happen if we let these companies and their DRM schemes take over completely: https://www.gnu.org/philosophy/right-to-read.html