Whether these are just lazy excuses or not, but let's be real for a moment.
Imagine someone, who's used to go to reddit.com, search for a reddit app in the app store, both of which have the same logo, design, etc... and use their username/password to login and browse the content.
almost every service, that people use for the last decades is based on this specific approach, except for emails. Even the TLD was always .com
Now imagine, how overwhelmed those people might feel, when you tell them "just come over to lemmy".
Lemmy, where? lemmy.com? Here's where you then start explaining the different instances, federation, etc..
the next question will be: where's the Lemmy app? Remember, the unified logo and design? well, good luck explaining that all lemmy apps are de facto third-party-apps.
Now, once they make it throug all of that, the next hurdle that will confuse the hell out of them are the communities scattered all across the instances.