You are correct in that it has a lot to do with the fun of creating a cartridge or working with a cartridge that isn't available from the factory. Part of it could also be pride of ownership too. I guess it could be something like restoring a rare collectible. When you are done, you will have something unique that is a labor of love. For some, there is a lot of satisfaction in that. Years ago, wildcatting was done more to fill a performance gap. Most of the cartridges that we use today started life as wildcats (25-06, 338-06, 7mm-08, 243Win, 22-250, 260, 270 Win, 280, 35 Whelen etc.). You are also correct that nowadays there are very few performance gaps so now it has to do with more minute details of cartridge design. I wanted a 338 Lapua but couldn't have one in a Savage so I opted for a 338 Edge. I could have settled for the 338RUM but the key word there is SETTLED. I don't like to settle.