To be fair not all of them are related to the slowed down iPhones, as some of the lawsuits are also pertaining to the recently-discovered Spectre and Meltdown security vulnerabilities, which according to one of the lawsuits filed alleges that Apple had already known about these vulnerabilities since at least June 2017, and should have disclosed these details to the public more promptly.
The complaint goes on to claim that Apple will most unlikely be capable of fully fixing the issues without their devices taking a performance hit. This was actually an issue as a developer recently took benchmarks of the iPhone before and after the release of the patch, and it was discovered that his device took quite a big hit in performance after applying the iOS 11.2.2 update.
This combined with Apple’s previous iOS release that introduced the slow down will no doubt mean that older iPhones will become even slower than ever, and it’s not hard to see why customers might be miffed about it.