They are increasingly being used as a tool to censor legal but unpopular websites. You can build your own website but if your domain name get canceled and tier 1 ISPs block you, you can’t do a lot.
KiwiFarms is the latest example. No one is claiming it was a wholesome site, but it was entirely legal in the US and yet the owner is having difficulties getting it hosted because even though they have VPS providers willing to host the site, tier 1 ISPs have blackholed the sites IP. There is no alternative to a tier 1 ISP. You can't run your own, the are the lowest level of internet infrastructure and if they are being weaponized for censorship than it's all over for a neutral internet.
There are 16 tier 1 ISPs which basically hold the entire internet in their control. Arguably these companies should be required to route any legal traffic.