I present to you my active library card collection.
So many things are available to you at a library. Lots of great expensive (and/or out of print) books, e-books, access to publications you love but for many reasons do not subscribe to.
Many things you do not need a library card for. (Such as wifi access). Many things you do (to borrow books, place books on hold, e-publication access, many databases.) What is very nice is that today you can even access many of these items from the privacy of your own home. If you end up like me you may memorize your card number. Of course I confuse BPL and NYPL numbers sometimes so it can be fun.
lazy busy, so you are just getting a few general links.