There is another reason to go custom - most of today's frames are not designed for everyday riding and include stupid marketing BS like shaped / curved tubes.

I wanted a bike with a top tube equal to the seat tube height, relaxed angles and longer chainstays whilst keeping the headtube short enough to allow a decent saddle to bar drop.

Couldn't find anything I liked that fitted the bill so I went custom. I will never buy another off the shelf bike.