It's really good for getting materials to level your crafters, EXP is plentiful from the Ishgardian Restoration crafts.
It also helps your server continue the Ishgardian Restoration efforts. Admittedly, we're not quite sure where those efforts will lead yet, but it seems like at the end of the day (somewhere down the line at some patch in the future maybe) it will unlock Ishgard housing on that server.
Otherwise? You do it for Skybuilder Scrips, which can be exchanged for cool stuff like glamour, minions (including a Cerberus pup), hairstyles, at least three different emotes (/read, /bread, /lean) and two mounts, including a pegasus. It's also the only way to get umbrellas, or the new Kupo housing items.
There's also some achievements related to it that end up giving two minions and a Kupo Crown. So if you care about any of that, then yeah, it's pretty worth it.