I use Fastmail's subdomain addressing [1] to sign up for services in a very similar manner. I'm certainly sympathetic to bad services abusing the privilege of having your email address. My contention is that while this is the purported benefit of mailinator.com, in reality many people use it to abuse services.

In other words, there's a big difference between using ikea@ and saastrial1@, saastrial2@, saastrial3@,.. and so on to keep signing up for trials with the same SaaS provider.

[1] -- https://www.fastmail.com/help/receive/addressing.html