Editing and montage makes you think that Kenobi lives in a cave
It is a well known fact that editing saved "New Hope" from being a very poor movie, maybe even worse then "Last Jedi" :D Unfortunately some things had to be cut, so we have a story with very sharp transitions in some parts, and Kenobi's house is one of them.
First, there is a part where old Ben saves Luke from Sand People in front of some caves. We were never shown how Kenobi got there, implying that he lives near by.
Next we have brief look at Kenobi's house. Unfortunately this is sudden, the trip to it is never shown, and after that we have an indoor scene - a very important one where Kenobi talks about the Jedi and Luke's father, Leia appears in a message, Luke mulls should he go with Kenobi or return home ... Therefore, people tend to forget this shot:
Also note that the walls in Kenobi's house are very rough, so it's hard to discern if this a house or a modified cave.
Luke makes the decision he is not coming with Kenobi. Movie cuts to Imperials and after that comes a scene where Luke and Kenobi discover dead Jawas. Again, it is never shown how did they get there, subconsciously implying that Obi-Wan and Luke didn't go far. Scenery in this scene resembles the scenery in the first scene (Sand People attack and rescue). So a casual viewer would conclude that after Kenobi saved Luke they simply hid in one of the caves (Kenobi's home) and after a while they emerged only to find the Jawas attacked and killed.