[isykt]

The books were obviously not wanted by the people who put them there, otherwise they would have kept them.

A single person reading a book they wouldn’t have otherwise is an absolutely miserable ROI for the materials and labor involved. It would be much more efficient to just offer the first person you meet a free book of their choice from Amazon.

[pests]

You don't have to keep things you like. It's okay to share them and give them away to others. It does not diminish how much you liked or wanted that item to begin with. By sharing it, you are trying to spread that want that you once had. I admit this isn't the case always, but sometimes.

Eh - whats the harm? Not everything needs to have a positive ROI.

[isykt]

“What’s the harm?” is just turning the question around because the original question — “what’s the benefit?” — doesn’t have a satisfying answer.

If you want to reduce it down to “LFLs make people with extra books feel good” then, great, it’s obviously a resounding success, as evidenced by all the articles of people who built them beaming.