Have a look at this section of the AWS Redshift documentation (also a columnar database) to understand the advantages of these types of systems: https://docs.aws.amazon.com/redshift/latest/dg/c_columnar_st...

Or the advantage of columnar file formats, like ORC or Parquet, for analytical queries. Normally you are only interested in a few columns.

Columnar formats allow for some pretty interesting optimizations with respect to filtering by rewriting and pushing down constraints / checks; and evaluating multiple of them simultaneously, pulling as little as necessary.