When you go and buy a comic book or paperback novel from your local bookstore, there is a clear understanding of ownership. You simply pay for the title, bring it home and it is yours to keep and loan out to friends as you see fit. When it comes to eBooks and digital comics the entire situation is more convoluted, 99% of the time you do not own the book you purchased, you are merely licensing it.
Amazon, Barnes and Noble, Kobo, Sony or any other company that has Digital Rights Management clearly states in the terms of service or in the licensing agreement that the customer does not actually have ownership of the title. In 2012 a Norwegian Amazon customer identified only as Linn had her Kindle access revoked without warning or explanation. Her account was closed, and her Kindle was remotely wiped. This resulted in all of her purchases simply disappearing.
Many online retailers like Comixology sell comic books, but all of the purchases are stored on the cloud. If their servers were to ever go down or the company goes out of business, over 200 million people would be out of luck. JManga closed down last year and existed solely in the cloud and in-app viewing of content. When they closed anyone who purchased comics were unable to read them anymore.
The clear lack of ownership with eBooks, eTextbooks, digital comics and manga is one of the barriers of further digital adoption. Encryption such as DRM (Digital Rights Management) puts barriers in place to discourage piracy but make the purchasers life a bit more difficult. Most companies do not have a e-lending program, which makes loaning the titles out to your friends impossible. If you have a massive library and move to a new country, you run the risk of your entire account being shut down and all titles disappearing.
Some companies are trying to make peoples lives a bit easier. The Harry Potter online bookstore, Pottermore, scrapped DRM, and instead went with Watermark Codes. SCI-FI publisher, TOR, has also abandoned DRM and lets people download full copies of the books on their computers and can be read with any 3rd party e-Reader.