> Can't they figure out what books to get without being told?

Probably not? People are not "being told" what to read, they are given some opinionated advice which they can then decide to follow or not.

According to Wikipedia, 275,000 books are published each year in the US alone [0]. Most people (even excluding the many that don't read) will read well under 0.01% of that. Deciding which books to read without taking advice from someone more informed would not be optimal.

Sometimes it makes a lot more sense to rely of expert advice than to just make all decisions on your own.

[0] https://en.wikipedia.org/wiki/Books_published_per_country_pe...