Smooth jazz is just another subgenre that appeals to a certain group of people. Along with "acid jazz" it's just one in a long line of disrespected styles.
How about the "soul jazz" that was popular in the 60s and 70s...Herbie Mann, Eddie Harris, Les McCann, Bobbie Humphrey, Roy Ayers, Donald Byrd, Hubert Laws, Earl Klugh, King Curtis, Ramsey Lewis, Vince Guaraldi or any number of CTI artists?
Or the organ combo explosion after Jimmy Smith came along in the late 50s...Groove Holmes, Shirley Scott, Jimmy McGriff, Johnny Hammond, etc.
Or the "honker" saxophonists who straddled jazz and R&B like Big JayMcNeely, Hal Singer, Lee Allen, "Sam the Man" Taylor, Sil Austin, Willis Jackson, Arnett Cobb, etc.
Consider that Chet Baker sold a lot more records where he was singing than the ones where he just played trumpet.
All that stuff was derided by jazz critics but sold a lot of records and was on jukeboxes and the radio. After hip-hoppers started sampling the grooves off those records, there's been a lot of reconsideration. Not all jazz has to be cutting edge, not everyone is Miles, Duke, Bird or Coltrane.