You may have noticed that there is no longer an option to have a physical disc shipped to you. So few people order physical discs now that it doesn't make sense to offer it as an option.
We think downloads are better for everyone. The only thing on the disc is the installer, and those are freely available on the web. You can get our current products from our downloads page, and our older products from this support article. These pages will always be available.
We frequently fix bugs, so discs quickly become out of date. Also, they have an environmental impact. Shipping requires the consumption of fuel, and discarded CDs end up in a landfill.
If you ever need to reinstall, we recommend that you get the latest installer from our web site. However, If you want to keep a copy of the installer, simply back it up with your other files.