haleivi: to support your point, the tiferes yisroel explains a mishna which speaks out against sichas yeludim, as speaking out against humor which is “light headed babble” and that good humor would be one which you can learn something from it.
on the other hand, we have some stories that really do not come to teach any apparent lesson. for example, a gemoro in shabbis which relates a story of a mother in law pulling the ultimate punking of her daughter in law by getting the daughter in law to light herself on fire. seems hard to find a lesson there. or a gemoro in bava kamma which says chanan bija who couldnt find someone to make change for an old zuz in order to pay someone half a zuz which he owed as a penalty to someone he hit so he fixes the problem by hitting the victim a second time in order to pay him a full zuz. lesson? or the story in sota where the gemara says ever since rebbe died there are no anuvim left in the world and rav yosef says “what about me?” looks like a joke for the purpose of a joke. there are other examples.
maybe its a cultural thing. i think if you look at real sfardishe baalei shiyur like rabbi yosef, ztl, there is humor spread out throughout the shiyurim. it plays a big role. seems to me that culturally, that part of the world had humor as a very regular part of life. conversely, rabbi yisroel salant, listed 13 important values in life and did not include humor as one of them. the gaon, who came from lita also refused to see idle humor in shas (and for example, explains rav yosef’s statement to be talking about someone named ‘anna’ and not that rav yosef was trying to be funny. and explains sasson and simcha to be teaching a deeper lesson.)
or maybe there are some that are like this (lesson teaching jokes) and some are like that (just jokes) and some of those that i fail to see a lesson in its because i havent delved into them enough. or maybe all of them have lessons. i am open to the idea that my theory is wrong and that i just need more convincing. i dont pretend that i am always right.