The easy install script relies on playbooks in the bench project. Newer versions of distros and system packages roll out faster than we can act. These often break installs.
The last time I was dedicatedly maintaining bench, Ubuntu 18.04 had just rolled out. We’d run the script each time a Frappe requirement has changed, or disappeared from PyPI, or any type of updates, new packages or updates available on the dependent PPAs. This wasn’t scalable to begin with, and it was a never ending loop of dependency management and maintenance. Club that with the number of distros the playbooks were aiming to solve the setup problem for.
Around the same time, @revant_one started working actively on the containerised install (frappe/frappe_docker) method. And it’s heavily tested and most up-to-date and reliable install solution at this point.
The “easy install” script still works for some versions of certain distros…I don’t use it as often as I used to before. Though I haven’t faced any problems off late, you may not use the same options I use for my setups. There’s a PR open to install v13 by default, but it’s not ready yet. The script is still not nearly as tested as it used to be. I added the note because people still try using it and when the setup fails, they don’t know what to do and they’re stuck. Manual setups seem to be much easier at that point 
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If someone can actively try to maintain the playbooks, maybe this would change. But it’s Frappe Docker ftw as of now.