There are a number of scenarios in Drupal 8 where you might notice your MySQL database size starts growing incredibly fast, even if you're not adding any content.
Drupal VM has been hitting its stride this year; after adding experimental Docker support in 4.5, Docker usage has been refined in 4.6 (with a more stable and useful
More and more sites are being built in Drupal 8 (over 160,000 as of DrupalCon Baltimore 2017!). As developers determine best practices for Drupal 8 site builds and deployment, they need to come to terms with Composer.