They can be. I haven't went to Summerfest in decades. Wisconsin State fair can have great concert acts.
Summerfest has some free concerts. The Concerts being held at a Amphitheater aren't free though. Some seating at BMO Harris Pavilion was free also.
Summerfest does a have admission day each year and this year was if you bring 2 jars of peanut butter, you get in free. This year though, 4 headliners were cancelled due to band members of having covid. One of those 4 headliners that canceled out was Ann Wilson, best known as lead singer of Heart. One of her band members had covid.
I have no idea with the Wisconsin Star Fair having acts cancelled outside of Toby Keith. Toby Keith is the only act cancelled so far, but that was caused by Toby having stomach cancer.