I think the poster understands the practical reason for SBC/BBC usage. It's all been reiterated. The rhetorical question "why another 350" has been answered by practical assessment and explanation. Which Rick already knew.
Other motors are interesting and different than the norm. Exceptional? maybe. There are lots of projects with odd ball motors stuck in, with homemade motor mounts, just sitting in the rain. Not hooked up or finished because things don't fit and no junk yard parts available.
We don't condemn anyone who wants to innovate, fabricate, contemplate and separate their build from the run of the mill builds. They will be back in short time.
There is so much time, work and expense building a truck, that practical is a useful project plan. Restoration or restomod.
Obviously by just answering why so many use SBC/BBC does not take away from anyone doing whatever they want. This forum is mostly practical and many members are interested in restoration to as close to stock as possible/feasible. So there is a bias. That's why we're here, that's why many joined. I always want to put a SBC/BBC in everything

John and Peggy say in their explanation of "What is a Stovebolt"........."regardless of what engine it has".