A greater percentage of reddit is younger than some of them realise. So many redditors are going to be used to new reddit, and plug-and-play services in general. Kbin and Lemmy look like old.reddit, and they require them to understand the concept of what a 'server' is to even get started. This is knowledge they've never needed before to use the services they want to use.
Imagine spending all your life eating McDonald's and then somebody told you homemade burgers are way better quality, taste better, cheaper, etc; then when you ask how to get a taste of those bad boys they start with informing you that you'd need to grill them. It's not hard, it's just new.