Oh I totally get that. But where there’s mayo, there’s no need for butter. And if you slightly toast the bread first it will mostly hold off the sogginess. And it’s only really a problem with basic sliced bread, some nice crusty or dense grainy bread will often hold up anyway.
To me, it’s the equivalent of something like deep frying bacon. Probably still delicious but not really necessary.
I would like to get behind To’s, but it’s a bit too similar to toes. I like the idea of toes in my sandwiches less than butter.