Because your competition will. You work so hard to differentiate your brand. Why would you allow your competitors to beat you in the search engine results pages (SERPs) because of the way they structure their protocol?
Because we’ll get better data in Google Analytics. Not all non-secure referral traffic gets accounted for properly in Google Analytics, so it gets lumped into the direct traffic source. However, Google already notes the importance of all secure sites, so you will begin to see more and more referral sources displaying in your acquisition reports. #winning
Because you can’t AMP without making the switch. Mobile is the future, and you need to make sure your content rises to the top of the search results, loading as fast as possible. Without a secure web address, you can’t revise your code to allow your pages to be accelerated mobile pages (AMP).
If you haven’t already switched from HTTP to HTTPS, you’ll notice that you probably haven’t taken any major hits in the SERPs just yet, but putting off this best practice is just delaying the inevitable. Be proactive and make the jump before your competition does, so you’ll be ready when Google starts to increase the weight of this in their search algorithm.
If I’ve written this post right, I’ve convinced you to make the move. Here’s some additional information from Google to help you along your way, and don’t forget to update your robots.txt file and update and verify with Google using Google Search Console (GSC).