The one time I can remember that SHIELD used Sentinels for a non-mutant purpose - to fight Kang in the KANG DYNASTY - it didn't end well. So it's honestly a surprise to me that they would even keep using Sentinels at all, after Onslaught AND Kang AND every other villain who has ever used Sentinels for their own sinister ends.
You could say the same thing about SHIELD using guns, though.