Kind of like the Northern People who moved into Texas in the early 80's (1980's) and wanted to build their houses out of adobe brick. It sucked when it rained, as yes they did do this. Silly people.
I'm not sure if it's the same reason, but I expect that suevite, which is the impact-formed mineral that the church is made of, is shot through with cracks and inclusions that allow water seepage and frost/ice cracking.