There a number of large benefits to gifted, not the least of which is it changes the character of a program/school. If you are surrounded by bright students with nerdy academic interests it's suddenly acceptable to nerd out on things. This single fact may be more valuable to the development of the student than the entire program itself. Outside of gifted, schools have substantial challenges with creating environments where academic excellence is encouraged and rewarded not only by the schools grading system but also by social behaviour of peers. While bullying has gone down, and acceptability of geeky interests have improved in the past 30 years there is still nothing close to a gifted program from encouraging and accepting academic excellence.
As someone who just barely missed the gifted cutoff, my schooling was much too easy and I basically never had to study for tests or exams. I ended up developing poor academic habits that ultimately hurt me when the difficulty got hard enough that intellectual horsepower needed to be combined with hard work. I think being challenged early and often would have changed this behaviour substantially. Even creating an environment where I wanted to be around other students enough to participate in more extra-curriculars could have helped. I worry that we are going to create a lot of bright but unmotivated students by offering years of programs that are too easy for them. There are consequences far beyond just having these students occasionally act out out of boredom and I think it's a very bad idea to create an educational culture that suggests bright people should be lazy. This is ultimately what the removal of gifted programs do because classroom teachers generally aren't given adequate prep time or other resources to properly offer enrichment. I've even known some principals who encouraged their teachers to not offer enrichment as it created problems in later grades when other teachers didn't offer similar enrichment and parents expected it.