DRM - digital restrictions management - is a collection of methods to try to "protect" "intellectual property" from being "stolen" or re-shared or re-used ways differing from the intentions of the "owner." DRM prevents legitimate uses and fair uses protected by law. Real pirates circumvent DRM - the only people it harms are those of us who try to obey the laws.
Libraries are between a rock and a hard place. For some materials, the only way to get electronic access is by agreeing to DRM. We like and heartily support vendors that do not use DRM for their ebooks but we're forced to deal with others.
I got an ad in e-mail this morning from O'Reilly bragging about no DRM. That might be true, but they do indeed use technical measures to prevent institutional subscribers from downloading books or printing more than just pages of notes. So don't believe them!
If you're interested, here's a page with more information: https://www.defectivebydesign.org/dayagainstdrm