I've read in another answer, that for bread stretch and fold and kneading is more or less the same. On the other hand, almost all of the pizza recipes say kneading and almost all of the bread recipes have stretch and fold. Is there a reason for this, or more of a tradition sort of thing or is just my sample of recipes very bad?
It is just a matter of your sample. "Kneading" and "stretch and fold" are not really the same thing - the actual relationship is that stretch and fold is a subtype of kneading. In some cases (mostly very high hydration), it is more comfortable than other subtypes, in others, any subtype will do. So, if a recipe directs the baker to just "knead", the baker will use their preferred technique, which might be stretch and fold. On the other hand, if a recipe author very much likes stretch and fold, they may write it into the recipe even if there is no technical need to prefer it over another technique. The baker may follow it, or decide to deviate.
So in the end, what gets written into the recipe is mostly a personal preference of the recipe author. And what gets done during baking is influenced by both the recipe and the baker. So the word choice is a bit random, and there is no reason to have one more commonly used in bread than in pizza or the other way round. If you noticed such clustering (and just "noticing" is actually not enough due to confirmation bias) then it is likely you got an unbalanced sample, which is a very common thing to happen.