I’m one of those people that strongly believe that if you enjoy a series then you should support it as best you can. Obviously buying the BD’s, figures, and art books can be a bit expensive. Supporting series via purchasing the LN’s and manga is much more realistic for people that don’t have much disposable income.
It’s a great way to boost the chances of your favorite series potentially getting sequels, OVA’s, or other types of spinoffs. Sometimes surreal shit might even happen, and you become friends with some of the people involved with the light novel, or in my case, the anime adaptation of your favorite series.