You know the midrash about how Avraham Avinu had openings on all four sides of his tent, so as to be able to more easily greet visitors coming from any direction? I wonder if that wasn't the only reason there were four openings. This suspicion is based on what I'm experiencing right now.
I have windows on both the east and west sides of my apartment. Normally a strong wind blows through one window and out the other, making it pleasant in the apartment despite the August heat and no air conditioning.
Today, however, there is no breeze and I'm sweating away just sitting in front of the computer. Annoyed at the situation, I happened to go into my bedroom, which has an open window facing north. There I encountered an extremely strong breeze! Clearly it would be best if the apartment had windows facing in all four directions. Then I would benefit from the east-west breezes, when those existed, and from the north-south breezes the rest of the time.
We know that Avraham was "yoshev petach haohel kechom hayom" - in the hot part of the day. That is exactly the time he would most have appreciated a breeze from whatever direction it might come. And so it makes perfect sense that he would have had openings on all four sides of the tent, if only for that reason, not just for reasons of hospitality.