Good question. I think the idea is to make things easier for people who don't want to or cannot verify signatures, sideload and add their apps to Obtanium. It's for people who want to have the AppStore experience but feel comfortable with just downloading an app as long as the app is signed by a well-known and trusted signer, at best by the app dev him/herself. At the same time you can see which people from your web-of-trust have already downloaded the app and thus also trusted the signer. In short, I think it replaces the signature verification which many users aren't capable to do and provides an appstore experience people are familiar with.