Forgive my ignorance but why would anyone want to build on a plot on a creative server when they can just build on singleplayer creative and not be restricted to tiny plots? I've never understood this.

Builder's Refuge is one. Even if you're not a member, you can get 75x75 and 501x501 plots with full access to Worldedit, Voxelsniper and several other tools.
The 2 possible disadvantages are that its hosted in North America, which can cause latency issues, and the very high base-level of builds on there, which can be very intimidating. In addition, some members may be rather arrogant about their skills towards people not as experienced.

sorry for the typo I meant to say are there *any* not are there amy. Sorry