I'm going to keep this short and sweet! It's only 5 reasons, after all, although there are many more.
- Upgrading a Drupal 8 site to Drupal 9 should be comparatively painless, unlike previous versions. Drupal 8 (D8) is the most future-proof version to date. The more you invest in your Drupal 7 site, the less you are investing in a long-term, future-proof site with which you can continually optimize in order to boost growth.
- Contributed modules are ready! You can either install the Upgrade Status module on your D7 site to see your personalized upgrade path, or take a look at the Contrib Tracker resources.
- D8 is built on a model of continuous innovation – it just keeps getting better and better in a way that Drupal 7 never did. For example, usability is continually improving as you can see in the animations here in Drupal 8.2, followed by more improvements in 8.3.
- Pushing changes to the live site is more reliable, using configuration management. This is a huge step in making Drupal 8 an even more professional platform and enterprise-ready.
- There is even a module to automatically upgrade much of your D7 code to D8: https://www.drupal.org/project/drupalmoduleupgrader
Our team is comprised of Drupal experts and community veterans. One of our team members has been developing and contributing to Drupal for 12+ years, and our CEO has been a member for 8+. We've done several D8 migrations and are a friendly, ingenious, highly-responsive team. Let's set up a call to discuss!