Total Tournament Appearances 1942-2023: 33
Sweet 16 Appearances
2005 - National Championship Game
2004 - Sweet 16
2002 - Sweet 16
2001 - Elite Eight
1989 - Final Four
1985 - Sweet 16
1984 - Elite Eight
1981* - 32 teams total, started in round of 16
1963* - Elite Eight, 18 teams total
1952* - Final Four, 16 teams total
1951* - Final Four, 16 teams total
1949* - Final Four, 8 teams total
1942* - Elite Eight, 8 teams total
Since the start of the 64-68 team field, Illinois has been to 6 Sweet 16 's in 38 tournaments held. That's 15%
The tournament started in 1939. Of the 84 tournaments held, Illinois has been one of the 16 or better teams standing 13 times... also 15%. (Six of those tournaments, Illinois started in the round of 16 or better)
So I guess this all comes down to what your defintion of "uncommon" is. Websters defines "common" as "occurring or appearing frequently."
Is 15% freqeunt?