I think it's because the programmers' of ASOS knew their could (would) be rapid fluctuations in temp based on design/automation. -- thus a 5 minute avg. Why it hasn't been reprogrammed to account for this is beyond me. But 99.9% of even weather people don't know about the 5 minute avg and it's almost like they don't want people to know. But that's just me.
Many times when I check the one minute screen as show above - it shows an "odd temp" for a minute that makes no sense under calm atmospheric conditions (from jet exhaust((no jet exhaust in below example)) or whatever but always in the high trend, never low) - many examples. Here's is one from last June at 10:30pm - and even with a 5 min avg- the "74" still messed with the temp as it went to 67- even "officially" which is obviously wrong.
Since automation of observing weather parameters (ASOS/AWOS early 1990's) - you cannot compare it apples to apples to non automation (instrument shelters/ manual 8" gauges etc, manual weather observations-- mainly pre 1990's. But that's another can of worms.