In addition to the (very valid!) tech demo aspects of this, there's also the huge public interest/public relations aspect. I've seen more articles and comments on Ingenuity than on any other part of this Mars mission. (Personally, I'm excited for the MOXIE instrument[1] - tech that's all but mandatory before human missions)

[1] https://mars.nasa.gov/news/8926/nasas-perseverance-mars-rove...