There are other ways of turning engines around if required. If you also don't have a roundhouse and just utilize an engine house, you really don't need a turntable. A simple wye track will also accomplish the same thing if you need. While having access to a turntable is nice, the length of a Garratt is not any longer than a articulated engine with a tender. And the fact that you can run a Garratt in reverse with no downsides to tracking ability proved well for the situations it was used in. That problem doesn't exist much in the US as we have many steam engine facilities with the ability to turn big engines around. Perhaps that's another reason why it's design wasn't picked up.
Personally, I think the look of the Garratts is really cool. I prefer the rounded end tanks versions over those with square end tanks on either end. The rounded tanks give a streamlined look. I think of them like the hammock version of a steam engine
A boiler hung between two sets of running gear is a cool concept and it worked very well for the railroads that used them.
It would have been really cool to see what a US version of a Garratt would have been, knowing that we loved to design big engines. Knowing that ALCO designed the Big Boys, one could only imagine how big and powerful they could make a Garratt.