NIP-05 is definitely useful. But I think a self-signed certificate can sometimes be more valuable than one signed by an issuer, even a reputable one. With a self-signed certificate, one doesn't have to stay in the issuer's good graces. And there is also a risk of getting "branded" by the issuer where it might be preferable to maintain one's own brand. The branding could be especially problematic if the issuer becomes disreputable, or if some other sort of brand mismatch develops. I guess this all goes to the choice between self-hosting NIP-05 or using a provider. One thing that NIP-05 does not do is protect against key loss or theft. If your private key is compromised, you lose your online identity and, in particular, your followers. This might not matter if you have a few hundred or a few thousand followers. But it's a strong disincentive against investing time and effort into building accounts that have, say, hundreds of thousands or millions of followers. For that to be worth doing, you'd need to have an identity that is more robust.