There could have been a lot of Imperial propaganda, censorship, and persecution of anyone talking or teaching about certain historical topics in those 18 years. People who remember or saw the Jedi in their prime know it’s better to keep their mouths shut. We see on Tatooine there are local spies and informants at work.

Luke knows about the Clone Wars, but seems to never have heard of Jedi or the Force. Unless Uncle Owen has been working overtime editing his nephew’s history books. 😉

There are probably several fatal altercations a week in the Mos Eisley cantina, (we see three in the space of half an hour in movie universe time) but the only one we see someone get the local troopers to check out is the one involving an old guy whipping out a lightsaber. Han is certainly in no hurry to leave after shooting Greedo.