I find it is expeditious to share via sharing sites when the photo count is 'reasonable'...a dozen, and/or the groups are spread into different states. But when I shoot events for relatives (like a grandaughter's First Communion over this past weekend), the photo count was 60 and waiting for 350MB of files to download is burdensome compared to burning them to DVD! And dropping the DVD in a DVD mailer via USPS is hardly burdensome in effort or cost.
DVDs declined because of tiny MP3 players (with inferior-to-DVD sound quality), and the capabilities of smartphone which are always in the pocket/purse, and because of the demand on thin and lightweight laptops. But there are clear advantages that should not be forgotten. It is a bit like SD in lieu of CF...folks have become ignorant to the inferior speed capability of (serial, one channel) SD compared to CF (parallel, 8 channel) yet our video is ever increasing in resolution and frame rate, and our pixel count is ever higher...taxing SD more and more!
CD's and DVD's have declined because it's a broadband world to a great extent and a 350 file is not much when you have a 100m internet connection. The installed base of optical drives has dropped significantly. Many new computers do not come with any optical drive. People sometimes have a USB connection DVD drive but they don't often use them. Thumb drives are so cheap these days that people share large collections of data using them. I know that's how I share things with my family. None of them have any optical drive except for a USB drive which they look at as a hassle to use.
Netfix and other video sites have made DVD's unnecessary for many. As for MP3's the high bitrate variety is all but indistinguishable from CD. For the purist there is FLAC. But let's not forget it's all digital even on CD's. Many think vinyl to FLAC recordings are often superior to CD depending on who makes the recordings usually. And there are even higher quality formats available also.
I have had a web server for sharing files for over a decade now. I only have a rudimentary web page up but it allows me to share whatever files I want with far fewer restrictions. The bandwidth is better also. I have gotten out of the video production business so I don't generally need to transfer gigs of material. If I do transfer to family members we use a thumb drive. I know optical media is cheap to use and mail but one thing is that over time optical media goes bad and data gets lost. I no longer trust the format to last more than a couple of years. Commercially produced media lasts longer but for file sharing it can lead to lost data if you count on storing on optical.