I always thought it was a lack of a functionality the fact that everytime I've uploaded my photos on my flickr account it was leaving behind the GPS coordinates, which most of the times it's not a problem because I don't use often the GPS of my Canon 6D, but the times I use it, like when I travel around Ireland or abroad, I really want to share the position of my photos, because it's easier for me to remember where I took that specific photo, but also for other photographers who are looking for locations to photograph.
And in the past days I've been uploading my photos of my recent trip in Iceland, and I couldn't understand why once I've uploaded the photos on flickr, the GPS data, which I can easily see on Adobe Lightroom, are lost on the upload process.
Until tonite. There's no lack of any functionality, it's all there, it's just disabled by default, and all you need to do is to check two things: the first one is if Lightroom is exporting the GPS coordinates in the Exif data of your photos, and the second one is to check if Flickr is reading this information when it uploads the photos on the server.
So, for to check the first step, you need to go to your Export window in Adobe Lightroom, under the Metadata section, and be sure that the option "Remove Location Info" is NOT ticked!

If this option is not selected, it means that everytime you export a photo with that settings, is going to save the GPS coordinates in the Exif data of your photos.

The next step is to check if Flickr is reading this information. So now you need to login into your flickr account, go to your account settings, and then go to the "Privacy & Permissions" tab, and under the section "Defaults for new uploads" you need to check if the option "Import EXIF location data" is set to Yes, otherwise the GPS information will be lost at the moment you upload a photo.

Bear in mind that this will not enable the GPS information for the photos you previously uploaded on your flickr account, but only from the moment you enable this functionality, if you want to set the coordinates for the photos you already uploaded you can only do it by using the flickr organize tool.